We are naturally inclined to look for a problem, figure out a solution and then move on to the next issue. Appreciative Inquiry takes the opposite approach. In AI, you are taught to look at what you did right, how you and your team made a difference. This is a difficult thing to do. It can be so effective, though! Why not think about what you did right and replicate it? Why focus on the one or two things you did wrong?
The thin book, is just that--THIN! It is an easy and quick read. Hammond wrote this as a manual to introduce you to the concept of Appreciative Inquiry. You will gain enough from this book to implement meaningful changes. If you are interested in learning more about AI, I recommend reading the original book written by David Cooperrider and Diana Whitney.