An illustrated guide to the mammals of the New World tropics, compact enough to slip into your daypack, with 29 color plates illustrating more than 200 species. It covers most Central and South American mammals. Even the author concedes that it's difficult to see many of the more elusive rain forest mammals but keep a close watch for the sloths -- they're marvelous, and not likely to escape in a hurry.  (GPS12, $32.50)