The Bread Bible by Rose Levy Berenbaum:
The single best reference for baking bread, while not all the author's recipes, this author does the best job of teaching difficult baking concepts simply.
The Bread Baker's Apprentice by Peter Reinhardt
Artisan Breads Everyday by Peter Reinhardt
Anything Peter Reinhardt does with bread is amazing, his books are standard reference works for most home and artisanl professional bakers. His breads are amazing.
The Il Fornaio Baking Book by Il Fornaio
If you want to learn about the Italian approach to making bread in America, this is the book to do it with. When these guys were a smaller company, they made some of the best bread you could find.