Phew! This book is bleak as hell, but overall, I really enjoyed it. It's gory and deeply unsettling. The physical and psychological anguish experienced by each character is relentless. The pacing is slow and meticulous but somehow manages to be consistently engrossing throughout. The "monster" in this book is refreshing in its originality. I found it much more disturbing than an actual monster, ghost, etc. And the constant shift in perspective was expertly pulled off. 

There were a few things that bothered me about this book. The biggest problem I have is when Jeff accidentally sees Stacy's breast and then contemplates  the differences and similarities between Amy and Stacy's nipples. I really hate when male authors include that kind of shit. The women characters are sexualized for no reason and in ways that the men never would be. Amy and Stacy are written as Madonna/whore stereotypes. I guess there's some "commentary" about this when Eric describes how Hollywood would write their story, but still, the only two women in the book are comparatively two dimensional and clearly written from a male perspective. The shallowness of the women and the references to their bodies really made this book go from 5 to 4 stars.
I thought the whole pretext for the group to be in the jungle in the first place was weak and could've been fleshed out more. 
I feel uncertain about how the Mayan community was portrayed. They are nameless, voiceless, and for our purposes basically interchangeable. And like the environment itself, the Mayan people are a lethal threat to our (white) main characters, with unknown motives. On one hand, the way the Mayans were presented felt realistic to how the main characters would view them. At the same time, it's hard to say where the characters end and the author begins.