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Casey Grimes #1

The Mostly Invisible Boy

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★ Silver, Wishing Shelf Book Awards!
★ Bronze, Readers' Favorite International Awards Contest!

This "wildly imaginative" (Book Pipeline) "splendid conception" (Kirkus) from upstart author AJ Vanderhorst celebrates the transformative power of courage, tenacity and a little skill with a battle-axe. Set in an alternate USA where monsters prowl, this debut novel is told from the perspective of mostly-invisible-but-still-hopeful Casey Grimes.

Eleven-year-old Casey is stubbornly friendly, but he's eternally the new kid at Vintage Woods Middle School. Students look right through him—and they're not faking. Casey doesn't know why he's mostly-invisible, but when he scales a colossal oak, he discovers a fortress in its branches. The forgotten sentry tree marks the border between his safe, suburban life and a fierce frontier.

Casey and his little sister Gloria infiltrate Sylvan Woods, a secret forest society devoted to ancient, wild things. Sky-high footpaths. Survival sewing. Monster control. Shockingly, people here actually see Casey—but being seen isn't enough. He wants to belong.

Keeping his identity hidden--while struggling to prove he fits--is hard enough, but Butcher Beasts have returned to Sylvan Woods after a hundred years. Trickery is under siege. As the monsters close in, and the fearsome Sylvan Watch hunts Casey down, he and his newfound friends must unearth abandoned magic, buried at the forest's roots...or be devoured along with everyone else, Sylvans and civilians alike.

A fast-paced middle grade fantasy/adventure book with all the monsters kids could ever hope for.

292 pages, Paperback

First published April 25, 2020

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About the author

A.J. Vanderhorst

4 books39 followers
AJ Vanderhorst has had many jobs, including journalist, paramedic, escape artist, and baby whisperer. One time in fifth grade, he built a traffic-stopping fort in a huge oak tree, using only branches and imagination, and slept there for a week.

Now he and his wife live in a woodsy house with their proteges and a ridiculous number of pets, including a turtle with a taste for human toes. This makes AJ an expert on wild, dangerous things—invisibility spells, butcher beasts, hungry kids, you get the idea.

He is the only author in the world who enjoys pickup basketball and enormous bonfires, preferably not at the same time. He and his family have drawn up several blueprints for their future tree castle. Visit AJ online at ajvanderhorst.com.

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5 stars
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Displaying 1 - 30 of 72 reviews
Profile Image for A.J. Vanderhorst.
Author 4 books39 followers
May 9, 2021
No stars from me for obvious reasons. :)

This is a book I've lived with for a long time...years now. I hope I can say this about every book I write, but: this one is close to my heart. If this book was a person, I'd describe it as feisty, whimsical, heart-on-the-sleeve and a little crazy.

My editors, beta-readers and kids have described it as "inventive, believably adventurous, full of heart, rollicking, vivid, a book you want to live in, witty, funny and scary."

Even though April 2020 wasn't a wonderful time to send a baby book out into the world, I'm overjoyed that you all have the chance to read it.
Profile Image for Autumn.
17 reviews5 followers
November 29, 2020
Holy Creeps!

'The Mostly Invisible Boy' was a pleasure to read. I received a copy in exchange for a honest review, so here we go!

In short: Casey Grimes is invisible. No one ever notices him, save the trees he climbs for solace. There he can feel at peace with the birds and nature. So when he finds a bizarrely huge Oak, he must climb it. When his parents get tickets to Jamaica and Casey and his sister Gloria are not invited (LOL) and their mysterious babysitter, Ms. Jones, is oddly approving of Casey's tree-climbing/fortress-finding adventures, he and Gloria return to the Oak fortress and end up in a massive adventure.

My Thoughts: (Possible Spoilers)

The real magic of this series is in the Sylvan world. Imagine an interconnected world of tree fortresses, bonfires, battles, and monsters. Throw a school up into those treetops and that's what this story offers. Of all the things in this story, I find myself most captivated with the creatures. Bog Creeps, Tree Shrieks. I don't know why, but the fanged rabbits were the coolest creatures to me. I thought the school was fascinating and detailed enough that it was believable. This is also created when other characters casually reference information in conversation the way real people do.

There was a wide variety of characters in this story with a range of personalities. Starting with the main characters, I found Casey to be easily likeable. He had enough self-doubt and concerns that when he thrust himself forward, it was compelling to watch. Gloria was a cute gem full of surprises. My other favorites were Jake McGusty the school reporter, 'Pink-Eye' Robert, and mysterious Ms. Crake.

I thought the prose was very animated. The story carried much of its energy due to the vivid imagery of the prose. I especially love the description of the parents getting into the taxi to head off to their trip. As I read it, I saw cartoons in my head. Although, at times I thought it got a little cluttered with detail, I think the prose was well handled. I don't read many stories that bounce off the page within sentences of chapter one.

'The Mostly Invisible Boy' is a thrill ride for those that love adventure, tree houses, friendship, wacky-worlds, and want to follow a new series.
Profile Image for Kori.
46 reviews
September 9, 2020
The Mostly Invisible Boy is a complete blast. While it is written primarily for a middle grade audience, the beauty of this story is that it is so engaging that any reader can enjoy it regardless of age. I am 35 and was on the edge of my seat for the story of Casey Grimes. An awkward 11 year old who quite literally nobody notices, Casey is thrust into an adventure beyond his imagination when he discovers an unusual tree fortress in the forest near his family's home. Little does he know that this discovery will send him on a life-changing quest to solve the mystery behind a fantastical hidden realm and introduce him to some new friends—not to mention some enemies. You will love these witty, exciting characters and their universe and will never want to leave. It's the fun, engrossing read you need for these difficult times and a great choice for kids learning at home who need a new book to enjoy.
1 review1 follower
May 21, 2020
This amazing story of friendship, loyalty, and courage is something to marvel at. AJ Vanderhorst is a great author! This book displays Casey's emotions as well as a feeling of being ignored. His love of climbing is also shown when he finds a giant and also magical oak tree. He later discovers a magical land and makes a new friend. Casey and his sister Gloria are surprised to find that the people in the most magical land they have ever been in absolutely hate magic! The sister-brother pair set out to bring the magic back and save the city from butcher beasts. Join Casey and Gloria Grimes while they go on this magical adventure! -Elena, age 8
1 review1 follower
May 21, 2020
I am not one of those guys who is crazy about fantasy. But this book made me think twice. For one, I am crazy about trees. I don't study them; I climb them and I love them. This book really hit the spot with tree ways, tree houses (that people actually live in), and tree schools. I also like that kids can have weapons (not guns, but swords, maces, etc.). If all books were like this, the whole world would be going crazy about books. I like the humor between Casey and his sister Gloria, and this was a big factor in my five star rating. This book was awesome. Coen, Age 11
7 reviews
May 21, 2020
Having spent my summers in the willow tree next door, this book resonated so well with me! I loved reading it myself and was eager to share it with my kids. This book is action-packed and filled with vivid descriptions, making it seem as though the world of Casey Grimes really is just a Sentry Oak away.
Highly recommend this book as a read-aloud for families as well as a great novel for middle-grade readers to devour on their own. It has fantastic sibling relationships, supportive parents, and tells a good and true story of finding one's place.
Profile Image for Amy Cato.
9 reviews
April 23, 2020
I couldn't put this book down! Engaging, humorous, and original, this book with its endearing characters is full of intriguing adventure and yet still feels riveted in reality of Casey's personal struggles with identity and how relationships work. I love that! I also loved the quality and fresh feel of the writing. Warning : you'll wish you could jump into the book for some of this tree fun before it's over.
Profile Image for Aidan James II.
2 reviews2 followers
May 24, 2020
Enchanting. Woods meet Magic in this impossible-to-put-down adventure. This has already been put in my top 25 all-time reads. In my eyes, this book could quite easily be compared with the greats. (Harry Potter, etc) But you can’t really say it’s much like Harry Potter. When Harry is practicing surprisingly-early romance, Casey is practicing true and whole friendship.
AJ Vanderhorst takes a lot of relatable struggles and relationships, and combined with enchanting writing, the help of mighty trees, hidden magic, and fierce monsters, The Mostly Invisible Boy is a 100% unique, 100% beautiful, 100% adventurous story.
Profile Image for Lousbookstuff.
258 reviews41 followers
June 16, 2021
You can find my full review for this as well as other books on my blog here

3.5 stars, rounded up to 4.

This is an absolutely adorable middle grade adventure with lots of tree climbing, a secret forest community and of course monsters to be dealt with!

Casey Grimes is 11 years old and he is invisible to the world pretty much all the time. The bus doesn't stop to pick him up, the kids at school see right through him and like any child he just wants to be seen.

Casey loves to climb trees and is fascinated by the forest by his house. One day Casey discovers a giant oak tree that he has never seen before. There is something special about the tree that he can't put his finger on but he is determined that he has to climb it and find out.

Upon reaching the top he discovers a whole new world that he never even imagined existed. A community of forest dwellers known as Sylvans who protect civilians like him from the monsters that dwell in the woods.

Casey, upon telling his little sister Gloria about this magical place that he has found ends up discovering that she is just as invisible as he is, a very special bond is formed between the two siblings and they climb the huge oak together. This then leads to meeting a Sylvan called Luci and they all become fast friends and have wild adventures together.

This book is amazing for children who want to lose themselves in another world, who enjoy nature and tree climbing and fighting monsters!

I loved the relationships between all the main characters. I found them all to be very sweet, believable and very relatable for children and even adults alike. Casey's journey to finding a place where he feels he truly belongs is one I think many can enjoy.

It is heartfelt, funny and very fast paced!

The pacing is my main criticism when it comes to this book. I would have loved to explore this forest world a lot more as I think there is so much more to see, learn about and enjoy. I didn't like how the book seemed to jump in time from one paragraph to the next without any warning. It left me feeling like I had somehow missed something. This is a common thing with MG books that I have read in the past though but it is something that bugged me so I felt it was worth a mention.

I was also not at all keen on Casey's parents and the strange nanny. None of these characters or the way they behaved made any sense to me at all.

Overall I found the book charming and very typical of middle grade stories in general. It was an enjoyable, fast read that I would recommend. 
Profile Image for Eileen.
1,822 reviews69 followers
August 13, 2020
Although this was a book written for middle school students, I found myself enjoying this quite a bit as the story took me into a magical domain adjacent to our own mundane world. Casey is a boy who is very much invisible to everyone except his immediate family, from the bus driver to the teachers to the kids in his own school. They don't bully him, they don't ignore him, they just don't see him. His parents end up winning a much-needed vacation and the nanny comes to town. Clearly she is more than meets the eye, except she is much more hands-off than Mary Poppins. But she is encouraging and supportive and even gives good advice, but she does not panic and clearly takes everything in stride. Casey discovers soon after the beginning of the book that his 6-year-old sister is just as invisible in her school but she has always been more cheerful about it which is why he didn't notice. When his parents go on vacation, he discovers this ginormous tree and that eventually draws him and his sister into an amazing adventure full of real danger, but also fun, excitement, adventure, and real friendships. I loved so much about this book, but I especially loved the 4 giant trees that were both the sentinels and the heart of Sylvan. A wonderful adventure and I look forward to reading more by this author! As an aside, I bet this would be a fun book to read aloud to your kids!

Thanks to #AJVanderhorst, #Booksirens, and #IntensePublications for this ARC in exchange for my honest review.
Profile Image for Evelina | AvalinahsBooks.
848 reviews438 followers
April 5, 2021
How I read this: Free ebook copy received from author

4.5 stars, rounded up

I really had fun with the Mostly Invisible Boy by A.J. Vanderhorst! The best thing about this book is that it’s going to be a series, so I won’t have to part with the characters. I’m definitely looking forward to more adventures to be had with Casey and Gloria, the brother and sister who find a whole world out there, hiding under plain sight, right next to their home.

But what I liked about this story was that it wasn’t just an adventure story – it’s also a story about loneliness and friendship. About being slightly weird and all alone, possibly not heard by anyone, possibly just sort of… Invisible. This theme starts with Casey being ignored by the people around him, and continues with his new friend Luci, who despite being in a completely different place, fares no better than Casey at being noticed or acknowledged much. All of this is between the lines, so it’s very subtle, but I liked this storyline.

You can feel from the start of the book that this wasn’t going to be a one-off adventure – or at least, it��s not meant to be. There’s a lot of set-up for adventures to come, and I personally can’t wait to see what this series turns into. Will there be more magic? Will there just be more combat? And what about that wacky babysitter?

If you want to read more on what I thought about this book, check out the full review here:

I thank the author for giving me a free copy of the ebook in exchange to my honest review. This has not affected my opinion.

Book Blog | Bookstagram | Bookish Twitter
June 14, 2020
Equally adventurous as it is meaningful. Reading Casey Grimes to my kids (10,8,7) lead to out-loud laughter, moments where they jumped about as if they were right there with Casey, as well as quiet moments of concern and thought. I have no doubt my kids have spent more time in the real woods behind our house as we have read about the woods behind Casey's!

While the magical world Vanderhorst creates is bound to draw any kid in with imaginative and fanciful elements, the book is also not merely silly antics. Vanderhorst merges his magical world with the stuff of real life: friendship, community, self-doubt, loss. On one page you find yourself giggling at the description of a crazy magical weapon or outlandish circumstance then on the next page you pause as you get the sense that you just read something that really matters, that really touched life.

Casey Grimes isn't just a better book, your kids (and you) will be better for having read it.
April 29, 2020
Beautifully written. AJ Vanderhorst’s writing style creates vivid imagery of his characters, the woods, their adventures. He provides heavy doses of humor, heart, and clever twists and turns that will reenforce the joys of reading for the Middle Grade Fantasy audience.

As the story begins, we see Casey Grimes lying in bed punching his pillow — tears flowing as he battles to overcome his devastating feelings of invisibility. Casey is drawing long uneven breaths as a TREE brushed his window — “twigs tapped the glass like knuckles” calling him to CLIMB.

For Casey, trees are his playground. Things don’t usually go well for him on the ground. This day he discovers “An ancient oak. Unthinkably huge”. As he begins to climb, he can feel his life begin to change. “Under his hands, a timber heart pumped sap through woodsy veins. He shook his head in disbelief.”

We all know about trees, right? Green leaves, brown trunk, found in forests. But how MUCH do we really know? Immerse yourself in this adventure with Casey and his sister, Gloria, as they infiltrate the woods and win the friendship of Luciana. Join the trio’s adventures where ancient Sentry Trees stand as the link the between past and present, between magic and science. Travel through this fantasy realm with the sword-wielding Casey as he learns to manage his new-found strength.

This beautifully imagined story creates a magical web of adventure, intrigue, spying, treachery, fights and relentless action in a universe filled with Fantasy, Faith, Magic, Trust and Friendship.
Profile Image for Laura  Miller .
68 reviews13 followers
April 30, 2020
I received an advanced copy of this book from the author because we have mutual friends. I am so incredibly glad I did! I have read quite a few books so far this year (50+ at my last count!) and The Mostly Invisible Boy is one of the best I’ve read recently. I understand there is to be a sequel and I’m already excited about the next book. Casey Grimes’ story is a middle grade adventure/fantasy novel. The main character is dealing with questions of identity and the struggles of being a new kid, like many kids might. But there is an added twist—he can’t be seen by his classmates. No one knows why. Then he ends up on an adventure he couldn’t have imagined, full of monsters, danger, friendship, and magic. The world building was solid, I could imagine the places and happenings with ease. I loved the characters. They were genuine and interesting and likable. I loved the sibling dynamic between Casey and his sister and the friendships with his new friends. I really hesitate to say anything is “like Harry Potter,” but if you love the hero’s journey and the school of magic elements from HP, I bet you’ll like Casey Grimes too! I highly recommend it. I bought the kindle book to send to my sister (she’s away at grad school) before I even finished my copy because I knew she’d love it too. She started it today and already likes it a few chapters in. About Mrs. Jones, she said, “I wish I had a babysitter like that!”
Profile Image for Frank Morelli.
Author 5 books113 followers
April 28, 2020
For someone who grew up as "the kid in the back of the class", I can truly say that AJ Vanderhorst has created a character in Casey Grimes who is so relatable, and so tangible to anyone who has ever felt invisible, that his presence alone in the story is enough to keep the pages turning. Add to that a delightful setting built around the magic of a unique tree fortress, terrifying monsters at every turn, and loads of adventure all flowing with Vanderhorst's dry wit, and you have yourself a must-read fantasy novel for middle grade readers.
Profile Image for Alex Norton.
Author 3 books8 followers
October 8, 2020
Fast-paced, lighthearted middle-grade fantasy fiction. A neglected boy with a slight visibility deficiency discovers an entire magical reality in the woods behind his house complete with kid warriors, monsters, and old magic that needs to be uncovered...what's not to like? Written perfectly for the age group it's intended for, I'd recommend it unreservedly for ages 9-12.

As an aside, it's nice to see a story where an 11-year-old-boy and his little sister have a loving, functional relationship. A lot of kid's entertainment these days contains an overabundance of pseudo-clever sniping and snidery between siblings.
Profile Image for Peter.
39 reviews1 follower
July 3, 2021
Inventive, gripping, great.

If you'd like to be transported back to what it feels like to be middle school, full of self-doubt and seemingly invisible, this is the book for you. Only, it's so much more than that. It's about finding a place you belong, but not knowing you'll be accepted.
It's about taking a bold step, unsure whether you'll succeed.
It's about how magic exists, and families don't always have to break up.

It's a fantasy, and it's got so many direct applications to real life.

And my brother wrote it, so that's neat.
May 24, 2020
Underneath all the crazy action and behind the amazing setting of this story runs clear character development that is compelling. This author takes children, or young adults, very seriously; he shows the growth of improbable friendships through challenges met together and fragile trust moving into comradeship in such a believable way that one hates to leave Casey, Gloria and friends at the end.
But don't grieve--a sequel is promised!
Profile Image for Tonja Drecker.
Author 3 books174 followers
August 13, 2020
Packed with imagination and magical adventure, this is a book to cuddle up with under the blankets and get lost in an exciting world.

Casey is eleven-years-old, would love to have some friends, but has a very strange problem. He's almost always invisible. At home, he's completely visible. When his parents win a sudden trip, he takes off into the forest to climb a tree, and what an odd tree it is! But other strange things are popping up, too. The babysitter isn't all that she seems, monsters are suddenly lurking in the forest shadows and a strange girl from another world speaks to him in his head. Soon, he finds himself in a magical world with dangerous monsters and an even more threatening war. There might be a way to save everyone, but only if he and his friends aren't captured first.

This is such a fun, exciting read. While it starts out with a very strange surmise, Casey's invisibility is only the beginning of the imagination in these pages. The author has understood what a thrilling adventure for kids should look like and created a very rich and enticing world. It starts out with something most kids love to do (or dream of)—climbing trees. But already here, things take off in wondrous directions as Casey discovers the most amazing platform with tons of secret closets...in the tree. The magic expands from there as another world opens up and the danger comes right along with it.

Many kids will understand how it is to feel invisible, sometimes, and what it's like not to be understood or accepted. Casey not only has problems at school and with his parents, but even in the magical world, isn't greeted with open arms. And yet, he stumbles on the magic of friendship and there's even the warming relationship of sisterly/brotherly love. He learns to trust himself and step past his own comfort zone. In other words, Casey is a character who is easy to relate to.

Not only was the imagination and fantasy in this book a real treat, but the author never talks down to the reader. This tale allows Casey to head into a true adventure, where the stakes are high, the danger real, and his goal is almost impossible to reach. It's the kind of read which will keep kids on the edge of their seat and dream of battling monsters and saving the world themselves.

I received a complimentary copy and enjoyed diving into this book quite a bit.
April 18, 2020
This book took many of my favorite childhood daydreams - adventurous tree-climbing, monster-slaying, mystery, and friendship - and breathed life into them. Casey Grimes and his sister Gloria make a hilarious and sweet brother-sister team, and the cast of characters they meet are compelling and believable. The world-building is fantastic: a secret world of monster-slayers, magical tree fortresses, and legends that I child-me would have yearned to enter.

While the book belongs to a huge and beloved genre of fantasy, magical school stories, A.J. Vanderhost adds to the tradition with great touches like a whole class of new and terrifying monsters, Sleepover Week, a survival sewing class, and many more. I look forward to the rest of the series.

I received an ARC of this book in exchange for an honest review.
Profile Image for Aya.
506 reviews758 followers
December 18, 2020
This is such a fabulous book for both children and adults. It was a great fantasy world for the children to experience and for the adults to remember their childhood again.

Casey was mostly invisible to everyone. He wasn't happy in his life. One day he entered a fantasy world with his sister unexpectedly. He built new friendships, killed monsters and found a whole new world.
The writings was fantastic, there werent any boring parts. The chapters were short and they made reading the book so much easier. The author did a great job creating a fantasy world for the readers.

I've received a free copy of the book from the author via VoraciousReadersOnly.
Profile Image for Dawn Sanford.
5 reviews2 followers
May 12, 2020
This is a great read. It's captivating from the start, no need to 'try' and get into it. It was difficult not to read it all in one sitting. It's av wonderful world and unlike anything I've read before. Looking forward to the next in ther series!
Profile Image for C. Gonzales.
755 reviews23 followers
June 29, 2020
Wow what a wonderful MG Fantasy book! This is a cute story, fun to read, and not just for kids. I liked the more complicated premise and the plot. All the characters were interesting, even the bit players. Good for anyone that enjoys reading light fantasy.

Full of non-stop action, it captures you and keeps you turning pages from beginning to end.
Profile Image for Asher.
1 review
May 24, 2020
A great read, filled with magic, mythical creatures, and massive tree forts. This book paints a clear picture of the world AJ has created. When you read this book, you can hardly believe that you won’t find the occasional bog creep in your woods.
1 review1 follower
May 24, 2020
One of the first books our family has read that all 7 of our kids clamor to start reading earlier each night so we can read more before bed! I have found stashes of treehouse drawings growing on sidetables. Read it aloud, read it alone, just make sure you read it!
Profile Image for Ezra.
1 review
June 12, 2020
This book is an amazing and exciting book! I love the way he makes it in a style that is not all literary but still really cool and exciting! I think that this is a book that is a fantasy but still so believable! I especially love the way characters in this book are different and have different views on things. Hail Casey Grimes!

Profile Image for Nora Delzelle.
Author 2 books9 followers
July 9, 2021
A truly great story!

This book is a wonderful snd exciting adventure story. I loved the themes of friendship and finding a place to belong. Kids will love this thrilling coming of age story.
Profile Image for TheBookDude.
94 reviews15 followers
June 23, 2021
The Mostly Invisible Boy by AJ Vanderhorst was an absolute delight to read!

The book is just right for young readers, but I think adults can enjoy it too due to some deeper meaning and the themes it touches on. I love the focus on trees and nature throughout. I think so many kids feel invisible at times and that is certainly the case of Casey. It makes his character so immediately relatable.

The book has everything you want for a quick get away into a childhood fantasy world, magic, friendships, monsters I loved it. Beautiful imagery throughout and very well written. Highly recommended.
Displaying 1 - 30 of 72 reviews

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