Here are a few books we have found useful during our dog training.

How To Speak Dog by Stanley Coren This is not a "how to book" as the title may suggest, we'd recommend it if you would be interested in learning more about K9 communication and interaction with human body language.
Cesar's Way by Cesar Millan Primarily this is autobiographical and gives Cesar Millan's story of life and coming to America.  There are some interesting techniques and pointers to be picked up.
Be the Pack Leader by Cesar Millan A much more purposeful guide on being a dog owner and pack leader.  Cesar Millan provides an instructional guide which many will find very useful.
"RSPCA" New Complete Dog Training Manual by Bruce Fogle This is a great general purpose and beginners guide to training your dog from a puppy and through some important stages and steps.