This book is not going to be the only Quigong book in your library. However, it is a useful one.
Simply, it's an introduction to Quigong in various forms, from exercises to medicine to martial arts. It's not the most consistent book, and there are times where one may wish for more detail or less. However, there's also enough good material on breathing, exercises, history, and what to expect when you get deeper into Quigong that it's worth the price.
If you're an experienced practicioner, it's probably not worth your time, though it may be good for helping others start out.