The Lost City of the Monkey God: A True Story by Douglas Preston
For hundreds of years there have been rumors of an undiscovered lost city deep in the jungles of Honduras. Explorers have sought it, and some (fraudulently, it turned out) claimed to have found it. But modern day explorers, using new imaging technology that can scan the jungle from the air and potentially identify non-natural structures under the foliage, have isolated a few promising segments of virgin jungle to search. Douglas Preston attends the expedition for National Geographic, and the team finds clear, definitive evidence of a lost civilization.
The first third of the book recounts the history of the legendary "Lost City of the Monkey Gods"--the previous attempts to find it, the skepticism about whether it even existed at all or that it wasn't just another Mayan ruin, etc. It's a really fascinating history. The middle third gets a bit dull, as it's mostly speculation about what this lost civilization might have been like and why it disappeared. Little actual archeological analysis has been done yet.
The final third picks up again, when about half of the team from the expedition come down with a variant of an Old World tropical disease that could be deadly. Their bodies all react differently, and many are treated by the National Institute of Health, which performs experimental research treatments. Really fascinating stuff. Recommended to those interested in exploration, lost civilizations, and deadly diseases.