Whirlwind, by David Klass
This is the second book in the Caretaker Trilogy, after Firestorm. In Firestorm, all-around normal guy, Jack Danielson, finds out that he has been sent from the future to save the world's oceans, thus averting an apocalyptic environmental hell a thousand years in the future. Despite feeling like he is not hero material, Jack manages to save the oceans and defeat Dargon, an evil Machiavellian bad guy from the future who is intentially destroying the oceans to make a lot of money. The book ends with Jack adrift on the ocean, alone, with no way of knowing if he can reclaim his once-normal life.
Fast forward six months, where Whirlwind picks up. Jack has made it back to his hometown in order to see his old girlfriend, P.J., who is the only remaining person left in Jack's life. Unfortunately, her parents, instead of welcoming him, call the police -- turns out that P.J. is missing, and everyone believes Jack is to blame. And even though Jack wants nothing more than to forget about his destiny, it won't forget about him -- the Dark Army comes for him at the jailhouse, and he narrowly escapes with the help of his old pal, Gisco (the telepathic dog from the future, and yes, it does make sense when you read the books). In order to find P.J. and avert another ecological crisis, Jack has to travel to the Amazon rain forest, where Dargon's father has taken P.J. in revenge over the murder of his son. This man is even more dangerous than Dargon was, and is destroying the rain forest in order to wreck the positive changes Jack made in the future when he saved the oceans. But that isn't the biggest problem. The biggest problem is that Jack cannot defeat this man -- another time traveler, hiding in the present, is the only one who can. Jack must find this mysterious person in order to save the girl he loves and stop the destruction of the rain forest before the damage to the future is irreparable.
Just like the first, this book is scary, suspenseful, humorous (Jack and Gisco especially are very sarcastic), and absorbing, while conveying an important ecological message that rarely comes off as preachy or didactic. We will have this book available in the library soon, but until then, read up on Firestorm at the New York Review of Books, or read about how David Klass got his information on the rain forest from this Greenpeace blog.