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Undying Mercenaries #24
Demon World
When Earth's colonies go silent, Legion Varus drops onto Kepler-62 expecting a routine investigation. Instead, they find something far worse than death.
The colonists aren't dead—they're changed. A new kind of enemy has arrived in Province 921, microscopic invaders that transform humans into perfectly coordinated killing machines. These "Demon" parasites don't just control minds, they improve them, creating an army that works with terrifying efficiency.
As cities fall and soldiers turn against their own, Centurion James McGill discovers he's mysteriously immune to infection. But immunity comes with a price. To save humanity from becoming pawns of a new Galactic species, McGill must navigate a web of seduction, betrayal, and impossible choices.
Some invasions come with warships. Others come with a whisper, a touch, and a promise of something better. The question what happens when the enemy might be right?
DEMON WORLD is the latest action-packed entry in B.V. Larson's bestselling Undying Mercenaries series.
The colonists aren't dead—they're changed. A new kind of enemy has arrived in Province 921, microscopic invaders that transform humans into perfectly coordinated killing machines. These "Demon" parasites don't just control minds, they improve them, creating an army that works with terrifying efficiency.
As cities fall and soldiers turn against their own, Centurion James McGill discovers he's mysteriously immune to infection. But immunity comes with a price. To save humanity from becoming pawns of a new Galactic species, McGill must navigate a web of seduction, betrayal, and impossible choices.
Some invasions come with warships. Others come with a whisper, a touch, and a promise of something better. The question what happens when the enemy might be right?
DEMON WORLD is the latest action-packed entry in B.V. Larson's bestselling Undying Mercenaries series.
- GenresScience FictionAudiobook
502 pages, Kindle Edition
Published August 17, 2025
289 people are currently reading
66 people want to read
About the author
B.V. Larson
135 books1,529 followersBrian Larson is an American science fiction and fantasy author
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Displaying 1 - 30 of 39 reviews
November 23, 2025
Tired format needs wrapping up!
The series has become locked into a particular plot format and has lost its edge and humour to some extent. It starts with James in his shack…an unexpected visitor or emergency recall…some opportunistic sexual encounter with a major character… a dressing down for no particular reason…a mystery to solve in a far flung region of space…bumping in to Galina Turov who is usually cock blinking his latest squeeze…a disastrous and unlikely training montage on Green deck…another dressing down…a calamitous campaign with more twists and turns and lots of unnecessary success for the opposition only for a fluke that normally ends the drama…another dressing down…sex in the shack…etc. etc.
The series has become locked into a particular plot format and has lost its edge and humour to some extent. It starts with James in his shack…an unexpected visitor or emergency recall…some opportunistic sexual encounter with a major character… a dressing down for no particular reason…a mystery to solve in a far flung region of space…bumping in to Galina Turov who is usually cock blinking his latest squeeze…a disastrous and unlikely training montage on Green deck…another dressing down…a calamitous campaign with more twists and turns and lots of unnecessary success for the opposition only for a fluke that normally ends the drama…another dressing down…sex in the shack…etc. etc.
September 4, 2025
At this point, the story is less about big battles and more about how McGill can wriggle his way into—and out of—trouble. He’s slipperier than a greased fish.
We get the return of a familiar villain here, though I felt they were dispatched a little too quickly. In the previous encounter, there was more tension: McGill had to think fast, run hard, and rely on luck. I miss that style of conflict—it had more bite.
I can’t help but wonder, given where this book left our hero, if there’s more to uncover about the Demons and their agenda. Perhaps the next book will finally address where this thread is going. What I don’t want is a detour through a throwaway world. The Demons’ arc is the most intriguing part of the last book for me—and I want more of it.
At this point, the series feels like it needs to take a big leap forward. Either James drags Earth out of the Galactic doghouse, or he heads to the Core Worlds (hopefully with Seven in tow) to shake up the empire.
We get the return of a familiar villain here, though I felt they were dispatched a little too quickly. In the previous encounter, there was more tension: McGill had to think fast, run hard, and rely on luck. I miss that style of conflict—it had more bite.
I can’t help but wonder, given where this book left our hero, if there’s more to uncover about the Demons and their agenda. Perhaps the next book will finally address where this thread is going. What I don’t want is a detour through a throwaway world. The Demons’ arc is the most intriguing part of the last book for me—and I want more of it.
At this point, the series feels like it needs to take a big leap forward. Either James drags Earth out of the Galactic doghouse, or he heads to the Core Worlds (hopefully with Seven in tow) to shake up the empire.
September 3, 2025
I’ve read every one of this series and still enjoy them. Mostly. The last two have suffered from an apparent lack of any proofreading or editing.
Multiple times you would read the same sentence in two adjoining paragraphs. Additionally there were a number of repeated conversations that seemed like the author had forgotten he already wrote them.
Finally, need a little more coherence in the plot. Too many things are just glanced over or make no sense at all.
Hoping the next one is written better.
Multiple times you would read the same sentence in two adjoining paragraphs. Additionally there were a number of repeated conversations that seemed like the author had forgotten he already wrote them.
Finally, need a little more coherence in the plot. Too many things are just glanced over or make no sense at all.
Hoping the next one is written better.
September 8, 2025
I have read every book in this series from the start. I can honestly say I have enjoyed them. Until now. For the first time ever I found myself contemplating not finishing this one. It just didn’t seem to measure up to the other one’s. The story seemed to just meander along.
It may be because there are many to compare it to. Or because of the length of time between books. But this didn’t present the same zip in the character that I’ve seen before. I will admit I continued on because of my experience with the Authors efforts prior to this book. I can hope the next installment will prove up to the standard of the previous volumes.
It may be because there are many to compare it to. Or because of the length of time between books. But this didn’t present the same zip in the character that I’ve seen before. I will admit I continued on because of my experience with the Authors efforts prior to this book. I can hope the next installment will prove up to the standard of the previous volumes.
August 21, 2025
I did not see that coming…
Larson, if you don’t complete this story before I die, I’ll haunt yet ass.
You feel me, writer guy?
If that IS your name… 😉
Larson, if you don’t complete this story before I die, I’ll haunt yet ass.
You feel me, writer guy?
If that IS your name… 😉
September 12, 2025
And these books just keep on coming! We’re up to 24 now and I’m amazed by the amount of imagination that goes into creating each one of these books. This one is one of the better ones because it has an actual true mission that caused the Legion to act even though James McGill is still among them! As you’ll recall, James McGill was caught in a little bind during the last book. His family, well, Etta, her husband and child, William, are now living on Rage world which is a Rebel world according to the Earth leadership. They are not welcomed on Earth and McGill understands the feeling because he doesn’t support this rebel cause one bit.
Still, it’s family he’s concerned about. He did his part by killing the Rebel Commander Armel and taking his sword. So now he’s considered the “Hero of Rage World” because that pretty much stopped the rebellion in its tracks. That mission was over and he had just about forgotten all the troubles it brought when he had a late night visitor to his shack in Georgia. That’s not all that surprising since James has had numerous late night visits by various females and this was no different, except this female was his daughter Etta! She definitely shouldn’t be here and James told her that much as soon as he recognized who she was.
What she was doing there was to attempt to retrieve Armel’s consciousness. See James had taken Armel’s consciousness just after he killed him by tapping his tapper against his own. That consciousness was now securely stored with McGill for all eternity unless James found some reason to let it go. Etta was there to retrieve it or at least try. James wasn’t in the mood to just give it to her so they made an agreement that Etta and her family had to come to the farm on Earth for Thanksgiving to satisfy Jame’s Mother and Etta’s Grandmother. If she did that, then James said he’d give by Armel’s consciousness.
But, during this conversation, James was notified of an emergency alert recalling all Legion Varus soldiers. So, he had to pack up and go. This is where his new mission gets started, although James manages to get sidetracked on several occasions. It seems like something has gone wrong on one of Earth’s colonies. James wasn’t sure which one but he soon found out during one of those boring high-level mission briefings he had to attend. It seems that this colony had stopped all communications with Earth. Satellite surveillance showed that everything on the colony planet seemed to be working just fine, except the colonist weren’t talking to Earth. It was also noted that this colonies output of mined resources was drastically increasing. They were shipping out tons more raw materials than in the past and nobody could figure out why. It seemed as though the colony had gone to a twenty-four hour production cycle and everyone was involved.
Yet, there had been a colony ship that had escaped just prior to all this starting. The Earth satellites had observed this ship leaving the planet with smaller ships chasing after it as though to stop the occupants from escaping. But, escape they did and now two of those colonist were down in Blue Level being looked after. Blue Level was a quarantine level for all kinds of hazards. McGills history with handling aliens and such was know to even Consul Wurtenberger. So he ordered McGill to go down to Blue Level and find out what was going on with these colonist. Wurtenberger wanted to know if this was some kind of rebel action or if these colonist were infected with something strange and McGill was the guy to find out.
So, McGill reluctantly went down to Blue Level and gets to meet Megan. Now McGill has some strange attraction with women of all kinds. Yet this Megan seemed just fine to McGill. Now the other colonist was a huge dude who had obviously been a miner. McGill found out soon enough that this big guy was even stronger than he looked because he attacked McGill for no reason and his attack was faster than a normal human. He was also much stronger than possible and almost choked McGill to death. But McGill never goes unarmed so he took the knife out of his boot and was able to stab the brute in a fatal area. As the guy was lying on the floor, something like a metallic slug came crawling out of his ear. James immediately stomped on it, smashing it dead! That made the biohazard personnel very unhappy.
Long story short, McGill develops a relationship with Megan who doesn’t seem to be infected with whatever is controlling her fellow colonist. Further, McGill finds out that several more colonies have cut off communication with Earth, but are still producing whatever trade products they used to produce at an alarming rate. So, Legion Varus is ordered to go and to an investigation as to what is happening. McGill is alarmed by the number of new colonies that Earth has now established. He knows that legally, Earth was only allowed to establish three colonies, but now it seems as they have some seventeen colony planets. He hopes the galactics don’t find out about this!
So now we’re going to deal with an entirely new alien species. Their origin could spell serious trouble for Earth. They are also almost impossible to destroy without destroying the humans they inhabit. There’s going to be a lot of killing in this book, but it looks like humans are killing their own kind. Will they be able to do this for long?
Hopefully, this isn’t the last book in this series although it has gone on for quite a while. Still, we’ll just have to wait to see if a new one comes out eventually.
==[Note: As of 12/03/2023, this will not be published on Amazon since I have been banned from posting reviews for some unknown reason. Once the ban is lifted, assuming it does get lifted, I’ll go back and post this to Amazon.]==
Still, it’s family he’s concerned about. He did his part by killing the Rebel Commander Armel and taking his sword. So now he’s considered the “Hero of Rage World” because that pretty much stopped the rebellion in its tracks. That mission was over and he had just about forgotten all the troubles it brought when he had a late night visitor to his shack in Georgia. That’s not all that surprising since James has had numerous late night visits by various females and this was no different, except this female was his daughter Etta! She definitely shouldn’t be here and James told her that much as soon as he recognized who she was.
What she was doing there was to attempt to retrieve Armel’s consciousness. See James had taken Armel’s consciousness just after he killed him by tapping his tapper against his own. That consciousness was now securely stored with McGill for all eternity unless James found some reason to let it go. Etta was there to retrieve it or at least try. James wasn’t in the mood to just give it to her so they made an agreement that Etta and her family had to come to the farm on Earth for Thanksgiving to satisfy Jame’s Mother and Etta’s Grandmother. If she did that, then James said he’d give by Armel’s consciousness.
But, during this conversation, James was notified of an emergency alert recalling all Legion Varus soldiers. So, he had to pack up and go. This is where his new mission gets started, although James manages to get sidetracked on several occasions. It seems like something has gone wrong on one of Earth’s colonies. James wasn’t sure which one but he soon found out during one of those boring high-level mission briefings he had to attend. It seems that this colony had stopped all communications with Earth. Satellite surveillance showed that everything on the colony planet seemed to be working just fine, except the colonist weren’t talking to Earth. It was also noted that this colonies output of mined resources was drastically increasing. They were shipping out tons more raw materials than in the past and nobody could figure out why. It seemed as though the colony had gone to a twenty-four hour production cycle and everyone was involved.
Yet, there had been a colony ship that had escaped just prior to all this starting. The Earth satellites had observed this ship leaving the planet with smaller ships chasing after it as though to stop the occupants from escaping. But, escape they did and now two of those colonist were down in Blue Level being looked after. Blue Level was a quarantine level for all kinds of hazards. McGills history with handling aliens and such was know to even Consul Wurtenberger. So he ordered McGill to go down to Blue Level and find out what was going on with these colonist. Wurtenberger wanted to know if this was some kind of rebel action or if these colonist were infected with something strange and McGill was the guy to find out.
So, McGill reluctantly went down to Blue Level and gets to meet Megan. Now McGill has some strange attraction with women of all kinds. Yet this Megan seemed just fine to McGill. Now the other colonist was a huge dude who had obviously been a miner. McGill found out soon enough that this big guy was even stronger than he looked because he attacked McGill for no reason and his attack was faster than a normal human. He was also much stronger than possible and almost choked McGill to death. But McGill never goes unarmed so he took the knife out of his boot and was able to stab the brute in a fatal area. As the guy was lying on the floor, something like a metallic slug came crawling out of his ear. James immediately stomped on it, smashing it dead! That made the biohazard personnel very unhappy.
Long story short, McGill develops a relationship with Megan who doesn’t seem to be infected with whatever is controlling her fellow colonist. Further, McGill finds out that several more colonies have cut off communication with Earth, but are still producing whatever trade products they used to produce at an alarming rate. So, Legion Varus is ordered to go and to an investigation as to what is happening. McGill is alarmed by the number of new colonies that Earth has now established. He knows that legally, Earth was only allowed to establish three colonies, but now it seems as they have some seventeen colony planets. He hopes the galactics don’t find out about this!
So now we’re going to deal with an entirely new alien species. Their origin could spell serious trouble for Earth. They are also almost impossible to destroy without destroying the humans they inhabit. There’s going to be a lot of killing in this book, but it looks like humans are killing their own kind. Will they be able to do this for long?
Hopefully, this isn’t the last book in this series although it has gone on for quite a while. Still, we’ll just have to wait to see if a new one comes out eventually.
==[Note: As of 12/03/2023, this will not be published on Amazon since I have been banned from posting reviews for some unknown reason. Once the ban is lifted, assuming it does get lifted, I’ll go back and post this to Amazon.]==
September 9, 2025
More.of the same
If this was book one it would be ok, being book 24, there are too many repeats of previous stories, not the whole story, just bits and pieces
As ever the book revolves around McGill. The first 50% of the book is about him, his personal life and pretty much anything other than Demons and Demons World
Once we get to engage with the Demons, it follows the same formula of McGill ending up in the wrong place at the wrong time and by the end saving the day by some fluke that even he doesn't understand
The ending really makes little sense, the Demons inform on Humanity to the Galactics and then decide to save us from them. This I'm guessing will be book 25
If this was book one it would be ok, being book 24, there are too many repeats of previous stories, not the whole story, just bits and pieces
As ever the book revolves around McGill. The first 50% of the book is about him, his personal life and pretty much anything other than Demons and Demons World
Once we get to engage with the Demons, it follows the same formula of McGill ending up in the wrong place at the wrong time and by the end saving the day by some fluke that even he doesn't understand
The ending really makes little sense, the Demons inform on Humanity to the Galactics and then decide to save us from them. This I'm guessing will be book 25
October 10, 2025
Space Mary Sue gets a new girlfriend and this time she is part space goo. there is a big battle where a bunch of war crimes are committed and he brings his space goo girlfriend home to Georgia.
he also notices the butt of his boss multiple times.
having caught up to the author and am now waiting the 3-6 months between books. I can say that these books are more enjoyable if you give a bit of a break between them. the repeated themes and wooden characters become less noticable in small doses.
he also notices the butt of his boss multiple times.
having caught up to the author and am now waiting the 3-6 months between books. I can say that these books are more enjoyable if you give a bit of a break between them. the repeated themes and wooden characters become less noticable in small doses.
This entire review has been hidden because of spoilers.
January 1, 2026
These books have been bad for at least 15 volumes now. They are repetitive, juvenile, and FULL of plot holes. The editor seems to have given up on this one as well. There were plot points repeated no less than 3 times in the same chapter toward the end. They are sloppy. And the series keeps descending further into drivel. I honestly can't understand why I am still reading them. I think it's a sunk cost fallacy at this point. The reason these books have such high ratings is because the only people reading them at this point are deeply troubled. On reflection, I might need to talk to someone.
October 21, 2025
Essential Twist
And what has been a pretty stagnant universe with the playing deck of Galactic pretty well understood versus an earth mentality shifting priorities aside trying to establish the wellness and essential proclamation of a unified leader as serious enough of a debate to embrace the status quo. Finally, we have a shift! And it’s significant with a major central race, focusing not on the individual contributions, but the global contributions of the one.
And what has been a pretty stagnant universe with the playing deck of Galactic pretty well understood versus an earth mentality shifting priorities aside trying to establish the wellness and essential proclamation of a unified leader as serious enough of a debate to embrace the status quo. Finally, we have a shift! And it’s significant with a major central race, focusing not on the individual contributions, but the global contributions of the one.
October 24, 2025
the plot was really cool and built on the established lore but the author I felt sort of belted it out without proof reading it. Spelling mistakes and sentences that didn't make sense including repeating things. I also wish there was a bit more, half the book was before he got to the planet and he wrapped it up in a predictable way. I like how the character itself is changing though and exciting to see how he develops
December 1, 2025
McGill Soldiers On
Another thoroughly entertaining entry in the Undying Mercenaries series. Larsen also introduces a new character: a woman, enhanced by a previously unknown bio-mechanical galactic race, who beguiles McGill and seems likely to complicate McGill’s future efforts to save humanity from annihilation by Earth’s galactic overlords. Tune in to Larsen’s next installment of McGill’s adventures; you’ll be glad you did.
Another thoroughly entertaining entry in the Undying Mercenaries series. Larsen also introduces a new character: a woman, enhanced by a previously unknown bio-mechanical galactic race, who beguiles McGill and seems likely to complicate McGill’s future efforts to save humanity from annihilation by Earth’s galactic overlords. Tune in to Larsen’s next installment of McGill’s adventures; you’ll be glad you did.
September 22, 2025
Cant wait for what's ahead
Its like the quantom version of galacic species. Making it possible to overcome the mogwa and the skay. The intelligent nanites are eerily similar to what humans will attempt someday. What's not plausible is the autocracy of the vastly superior core planets
Its like the quantom version of galacic species. Making it possible to overcome the mogwa and the skay. The intelligent nanites are eerily similar to what humans will attempt someday. What's not plausible is the autocracy of the vastly superior core planets
September 24, 2025
Another great Undying Mercenaries book!
BV Larson is one of the best writers in developing characters who capture your interest and leave you wanting to see their next adventure. I must say I'm trying to imagine how Earth and its Colonies are going to handle this new Galactic entity. Can't wait to see.
BV Larson is one of the best writers in developing characters who capture your interest and leave you wanting to see their next adventure. I must say I'm trying to imagine how Earth and its Colonies are going to handle this new Galactic entity. Can't wait to see.
September 27, 2025
It's like coming home after a long trip
Larson does such a phenomenal job keeping James McGill true to character. It's like reading about old friends at this point. This series has turned into a happy place in my life and I'm always happy to see a new book get released. Enjoy the adventures of the most Tylenol driven mercenary.
Larson does such a phenomenal job keeping James McGill true to character. It's like reading about old friends at this point. This series has turned into a happy place in my life and I'm always happy to see a new book get released. Enjoy the adventures of the most Tylenol driven mercenary.
October 11, 2025
Great new foe
It's exciting to have a new highly advanced player in the game. The fighting is intense as usual the dying is both terrible and funny at the same time just like past books And of course old McGill's hound dog like always. It is an interesting read and opens the possibility for many many more books in the future. Anxious to see how this story turns out.
It's exciting to have a new highly advanced player in the game. The fighting is intense as usual the dying is both terrible and funny at the same time just like past books And of course old McGill's hound dog like always. It is an interesting read and opens the possibility for many many more books in the future. Anxious to see how this story turns out.
September 28, 2025
Can't get enough of this series
I've never read a bad Undying Mercenaries book. Each one is fantastic and keeps to the tone.
Good laughs, interesting sceneries, and grea5 characters.
I've never read a bad Undying Mercenaries book. Each one is fantastic and keeps to the tone.
Good laughs, interesting sceneries, and grea5 characters.
October 6, 2025
Fun series
The action is great, it's fast paced. The main character matures a little bit but not much which is good! Haha I'll be starting the series again while waiting for the next one to come out.
The action is great, it's fast paced. The main character matures a little bit but not much which is good! Haha I'll be starting the series again while waiting for the next one to come out.
October 20, 2025
more more more
I always enjoy the Undying Mercenaries series. Old McGill sure has a way of getting out of trouble so I know he is bound to save Earth and all its colonies. Can't get enough. Write more.
I always enjoy the Undying Mercenaries series. Old McGill sure has a way of getting out of trouble so I know he is bound to save Earth and all its colonies. Can't get enough. Write more.
October 22, 2025
Good Read
Good Ol dumb McGill comes thru again. Secret politics, expanding real estate, and strange alien goings-on, pull McGill back to the forefront in a humanity ending battle for survival. What else could you ask for from McGill?
Good Ol dumb McGill comes thru again. Secret politics, expanding real estate, and strange alien goings-on, pull McGill back to the forefront in a humanity ending battle for survival. What else could you ask for from McGill?
October 26, 2025
demons
All of the author’s books in this series are great to read! But this one has an extra twist that makes it especially satisfying. I look forward to his next work in this series! Thank you!
All of the author’s books in this series are great to read! But this one has an extra twist that makes it especially satisfying. I look forward to his next work in this series! Thank you!
November 11, 2025
Great reading and entertaining
Great reading and entertaining throughout the whole book. Larson has done it again keeping me entertained enough to keep me from putting down the book before finishing!
Great reading and entertaining throughout the whole book. Larson has done it again keeping me entertained enough to keep me from putting down the book before finishing!
December 22, 2025
and a step further down the Galactic empire road james McGill and humanity goes while battling strange aliens. like any other book in the series it is an easy male fantasy without much depth. very enjoyable to turn your brain off.
January 11, 2026
I’m so glad Larson is writing his books again! After the Rebel World debacle that sounded like it was written at (the very) least with the assistance of AI. This was a great book with a new and innovative type of threat.
August 19, 2025
Another hit.
This is one of the best sci-fi series out there. Loved ever book and this one is no exception. Looking forward to the next.
This is one of the best sci-fi series out there. Loved ever book and this one is no exception. Looking forward to the next.
August 22, 2025
always a fun read
Ol’ McGill up to his old tricks somehow becoming way more important than he should be.
Good read great series of books always look forward to the next one
Ol’ McGill up to his old tricks somehow becoming way more important than he should be.
Good read great series of books always look forward to the next one
August 31, 2025
Faith Restored ..
I was starting to loose interest in the silliness of it all but I’m back on board with Demon World!
Nothing like a bit of complicated alien neural frisson to spice things up!
I was starting to loose interest in the silliness of it all but I’m back on board with Demon World!
Nothing like a bit of complicated alien neural frisson to spice things up!
September 1, 2025
Funny, enjoyable and thoughtful
September 7, 2025
Fantastic
One of the best books in the series. I can’t wait till the next one. It looks or a huge conflict is coming up and James is right in the middle of it.
One of the best books in the series. I can’t wait till the next one. It looks or a huge conflict is coming up and James is right in the middle of it.
September 9, 2025
Another great addition to the James McGill universe. Fast-paced, full of unexpected twists, and never boring. Larson keeps the series fresh and entertaining—already looking forward to the next book!
Displaying 1 - 30 of 39 reviews