The Beer Book

The Beer Book by Tim Hampson and Sam Calagione is a great reference for serious beer drinkers.  It has a lot of information on types and styles of beer and lists over 1,700 beers with a picture of their bottle.  The beers are separated by country and brewery and each beer has a tidbit of information and tasting notes.  If you like beer, you can spend a lot of time flipping through this book.