This is the fourth Sigma novel I have read, and, once again, I'm not sure exactly how I should "rate" the book.
On the one hand, there is a lot of obvious literary trickery going on--I believe Rollins keeps a deus ex machina handbook in his pocket while writing--and things that any reasonable reader knows shouldn't happen, happens.
On the other hand Rollins' books are a whole lot of fun; books that I really, really enjoy--I've read four of them, after all--and Rollins has a magnificent imagination and sense of the grandiose. I mean that in a good way.
Basically, Rollins' books are meant to be as much fun as a box full of kittens (soft and cuddly on the outside, full of claws and teeth on the inside--so mostly tons o' fun, but with inherent danger), and to this end he succeeds remarkably well. On the other hand his plots and action feel contrived, and it's hard for me to seriously contemplate giving the books more than three stars, and that's probably being generous.
None the less, three stars it is, because the characters, settings and action are so much fun, that rating his book anything less would be, in my opinion, criminal.
With this type of story the reader is, I think obviously, supposed to suspend disbelief, because if the reader does not suspend disbelief the reader will surely poke their eyes out with a red-hot poker before starting the third chapter. I don't mean to be harsh by saying that, because, as mentioned, I enjoy his adventures, but some of the devices and amazing coincidences challenge even my maximum-security-lock-down suspension of disbelief.
Rollins melds archaeology with science and political intrigue to create massive, globe trotting adventure stories. His stories--at least the ones I've read--take place in historical settings of world heritage value, and Rollins shows no apparent remorse at blowing them--the ancient, culturally valuable sites--to smithereens. Although I wouldn't want to see the destruction that Rollins rains down upon his settings happen in real life, it always brings a smile to my face to see him willing to sacrifice these monuments, even if it is only fictionally, to the greater cause of hard-core fictional intrigue.
The characters aren't quite three-dimensional, but are absolutely beyond typical two-dimensional characters. Of course I've had four books to get to know these characters, and that probably helps in my estimation of their depth, but, much like an ongoing, episodic television drama, more and more of the characters personal lives are being revealed. By now, I would be sincerely saddened if any of the main characters were to meet their demise, although I suspect that sooner than later Rollins will knock-off one of the on-going secondary characters. That's because I do believe that Rollins is a conscientious writer, and understands that death, even of a beloved character, is sometimes what a series needs.
So, yes, I do recommend Rollins' Sigma series of books to those who want an enjoyable, fun adventure, a quick read, interesting characters, archaeological mysteries, puzzles to be solved, explosions and gun play, back-stabbings, and, plain and simply, those who want a grand old time of classic globe-trotting adventure. In fact I strongly recommend the Sigma series.
For those who can't suspend their disbelief enough to stomach groan-inducing coincidences and some rather obvious plot twists, you should probably stay away.