As always, Nevada Barr, a former park ranger, delivers wonderfully vivid descriptions of the great outdoors; an abundance of colorful, well-drawn characters; a thoughtful and courageous female sleuth; an inside look at the National Park Service; and an intricate and suspenseful mystery. However, the most mysterious thing about "Endangered Species," set on an island off the coast of Georgia and involving the investigation of a plane crash caused by sabotage, is that the paperback has been extensively revised from the hardcover. Namely, a major character, an exceedingly unpleasant, repulsive person, has undergone a sex change! In the hardcover, Marty is a woman in her 50s; in the paperback, Marty is a man in his 30s. It's not just a matter of changing pronouns; dialogue and descriptions are altered too. For example, in the original version, Marty's long hair is "worn in pigtails like an aging Pippi Longstocking's"; in the revision, it's "worn in pigtails like Willie Nelson in his heyday." There must have been a compelling reason for such changes, since ordinarily paperback publishers don't even bother to fix obvious errors, such as referring to someone by the wrong name. I think the character works somewhat better as a woman, but whichever version you read, you'll likely find it a good, absorbing, entertaining whodunit.