One of the greatest books I have read is Culture Clash by Jean Donaldson. I don't think the name does the book justice, because the title doesn't begin to give even a hint of what it contains. She does a great job of explaining dog behavior and how to train your dog.
She divides the book into two areas. She starts out with explaining why dogs behave the way they do. She goes through all the common behaviors that dogs tend to exhibit.
The last section is devoted to training the basic commands. But it not just how to teach sit, she has divided the sections into the lowest level of sit to the more advance sit. First you teach the behavior then she tells you how to shape the behavior to the next levels.
This book is very complete in covering many of the different aspects of dogs and really it's not that long, but I found it so packed with information that I often had to read small portions. I felt like I had to let my brain process or digest the information. If you only buy one book about dog training I would suggest this one. If you would like to buy a used copy half.com is a great place to find a book at a great price.