The Ruins

Stephen King called this the book of the year in EW, and it's featured in the summer reading section of the July issue of O, Oprah's magazine. Both say it does for the jungle what Jaws did for the beach.

The Ruins by Scott Smith
In Cancun, Mexico, for a peaceful vacation, a group of tourists sets off in search of one of their group who disappeared during an excursion to some nearby Mayan ruins, only to come face to face with an insidious evil that threatens their very lives. By the author of A Simple Plan. 100,000 first printing.