There are not many sources for the westerner who wishes to explore the depths of pranayama.This book is an exhaustive look into the art of breathing.It is complete,it is detailed and technical and it comes from an acknowledged guru.It is more than any other "modern" guru or yoga organization has put out in book form about the subject.For anyone who wishes to investigate and practice pranayama this is the classic.
In my humble opinion, BKS Iyengar is the highest authority on Yoga of these days. You may not agree with me, no problem, but just open this book and you'll see that I might be right. Brilliant and clear explanation of Pranayama, step by step genuine method,theoretical background and a whole lot more, not even speaking about the illustrations. To be absolutly frank, this book alone is better than a semi-learned instructor, which are abundant here in the West. This book WILL change you! No gibberish of Hinduism, pure essense of Yoga!