One of the hundred books a year I read:

A former Special Forces soldier stumbled out of the Amazon jungle four years after he disappeared with the rest of a scientific expedition. Before he could explain what happened or how to locate the rest of the team, he died from his injuries. Nor did he have a chance to explain how he had regrown the arm he had lost in battle.

A new team of scientists, escorted by a dozen U.S. Army Rangers, sets out to find the lost party. They face hostile natives, an inhospitable environment, and deadly animals. As the clues mount for their target, so do the mysteries—animals never before seen and plant life thought long extinct. As their losses mount, they also come to suspect someone is stalking them. Their worry grows that they will meet the same fate as the first team—lost forever to the fates of the Amazon.