This book is a huge improvement on the manual supplied with the camera, and will certainly help most D80 users to understand when, where and how to use many of the settings. However, it too often strays away from explaining the camera, and into territory better covered by many other general photography / digital photography manuals (such as choosing subjects or framing). I was also not too impressed with some of the illustrative photographs.
Nevertheless, I would recommend the book if you've struggled with the manual.