"The Secret Language of Dogs" by Victoria Stilwell

Clearly written and full of pictures, this book is a must for all busy dog owners.  Tips will teach people how to have a happy dog that behaves well.  Communication is key in any relationship, and the author explains how dogs communicate with others.  Barks and body language are explained, as well as unusual behaviors.  The science of howling, pain, and aging are covered, too.  This book is honest and not a be-all-end-all.  For situations that are unique or hard to determine, the author recommends a visit to the vet.  My favorite part of this book is the underlying these of positive training as opposed to negative training.  Punishing dogs does nothing but cause pain, and the dog learns nothing.  To have a truly happy and well-behaved dog, reward good behavior instead of punishing bad behavior.  I love that.