In no particular order, here is a selection of some of my favourite books on yoga and qigong:

Living Your Yoga Judith Hanson Lasater

Bringing Yoga to Life Donna Farhi

Light on Life BKS Iyengar

Yoga The Spirit and Practice of Moving into Stillness Erich Schiffmann

The Heart of Yoga TKV Desikachar

Yoga Mind, Body & Spirit Donna Farhi

Rest and Calm Paula Hines

Brightening Our Inner Skies Norman Blair

Insight Yoga Sarah Powers

The Complete Guide to Yin Yoga Bernie Clark

Yoga for a World out of Balance Michael Stone

Qigong and the Tai Chi Axis Mimi Kuo Deemer