The Language of Yoga by Nicolai Bachman
I bought this book when I started getting serious about my Yoga practice. I had one instructor who regularly used both Sanskrit and English names for poses, and I wanted to get better at knowing what she was cueing when she used Sanskrit. It's a very helpful book, with CDS that offer pronunciation guides.
Living Yoga by Christy Turlington
This book was recommended to me by my favorite Yoga instructor as a good read for someone who wants to understand how to make Yoga a daily part of life.
Eat, Pray, Love by Elizabeth Gilbert
Gilbert's autobiography-ish book is more than just Yoga, but it's a huge part of her self-discovery. She almost makes me want to visit an Ashram and go hardcore... but I don't think I could handle sitting crosslegged for that long.