I myself am a proponent of deep breathing owing to my serious study of martial arts and I found this book a delight to read and reference for different techniques. While Lewis appears to have been primarily influenced by Yoga and Taoist techniques he includes observations from various commentators, including some Western breath control specialists. This makes the book extremely well rounded and I think everyone should be able to find something useful within the pages.
Breathing is an oft-neglected factor in Western approaches to health and vitality and there is a general lack of awareness within the personal development community. This book will explain why deep breathing is beneficial on different levels and how it will contribute to your growth as a whole person. Although it isn't written specifically for a martial artist, anyone with an interest in developing their skills and knowledge in this area will find the book useful. Breathing is of course considered important in many martial arts and this will round out your knowledge well; you will also gain a good awareness of several different breathing methods that you can use yourself or with your students to, at the very least, add some variation to what you are already doing.