Here are products I recommend. You can view further details and reviews about them by clicking on them and being taken to Amazon

Ashtanga Yoga: The Practice Manual

by David Swenson

I've had this one since 1999 and had it personally signed by David. It's one I come back to again and again. It's in a spiral bound format making it easy to practice with. It has decent sized black & white photos and covers the complete Ashtanga Primary & Intermediate Series with one posture per double page spread including modifications.

Yoga Your Home Practice Companion

(Sivananda Yoga Vedanta Centre)

The Sivananda Yoga system combines yoga postures, yogic breathing, healthy eating, meditation, and positive thinking. This full colour book covers all these elements including some wonderful vegetarian recipes and an array of classic postures with excellent 20, 40 and 60 minutes routines aimed at beginners, intermediate and advanced students.

Anatomy of Hatha Yoga

by David Coulter

This is a very thorough study of yoga science with a strong Western academic perspective of it's anatomy and physiology. It has lot's of black and white photos and detailed illustrations with anatomically precise terminology. At over 600 peages of dense text it's no quick read, but you can dip into sections on back-bending, etc.. and it will expand your knowledge every time.