I've been studying Yoga for about 40 years now, and have read dozens of books on the subject. I've even written a couple books myself! I thought I would share wth you some of my favorites--books that I go back to again and again.
At the top of the pile is Autobiography of a Yogi, the first book on Yoga that I read back in the late 60's. It's the incredible story of Paramahansa Yogananda's journey as a Yogi, full of mysteries, magic and fun. If you've never read anything about Yoga, this book is where to start.
The next book I think I read was Swami Satchidananda's Beyond Words. I had met Les Alexander at a retreat in 1975. Les and I clicked right away and this is what he was working on at the time-- compiling and editing the many talks Swamiji had given in the U.S. since arriving 10 years previously. Les called it "Swami's greatest hits"!