I would highly recommend The Yoga Bible by Christina Brown, published by Godsfields press.
It is a very informative yoga book, with lots of great photos to guide you into positions. I would not recommend it to beginners, as I think many of the poses in the book are better suited to advanced yoga students. I have given this book to a number of my students, who travel a lot, as the pocket size format is ideal for them.
While we are not looking for perfect poses, I think the photographs in this book demonstrate very good alignment and technique, and introduced me to a few poses I had not seen before.
This book does not adhere to anyone style of yoga, but certainly comes under the wide Hatha yoga umbrella.