Wondering what kinds of animal guidebooks you guys have! I picked up a pretty nice one from Barnes and Nobles last year that was only 15 bucks. Some decent art and facts inside.
"The Natural History Book" by Dorling Kindersley is very up to date as regards its classification and has an interesting range of species.
If I recall correctly some of the US editions are done in collaboration with the Smithsonian Institution.
The Princeton field guides are great. Helm also makes field guides but I've found that they overlap with Princeton's. I'm trying to collect all the older versions of the Princeton field guides because I like the old cover art better. So far I have the Birds of Kenya & Tanazania, Birds of Southern Africa, Birds of India Sri Lanka & the Maldives, and Birds of Southeast Asia. They're all great! Audubon Society field guides are fantastic as well and you can't forget the Smithsonian Handbooks series (formerly DK Eyewitness Handbooks). Of course Lynx Edicions Birds of the World & Mammals of the World are phenomenal as well (but I don't have any yet). I'm waiting for Lynx to make an online Mammals of the World like how they did for birds.