There is a wide variety of books, videos, and other resources available to the student of yoga.   Although useful information can be gleaned from almost any of them, if you are trying to avoid accumulating excessive books, these are a few high-yield resources that I feel merit owning and detailed study:

        Books:

          Light on Yoga, B.K.S. Iyengar
          Yoga: The Path to Holistic Health, B.K.S. Iyengar
          Yoga The Iyengar Way, Silva, Mira, and Shyam Mehta
          Yoga: A Gem For Women, Geeta Iyengar

        Videos:

          Yoga: Alignment and Form, John Friend

          The Yoga Journal Practice Series, Patricia Walden, Rodney Yee

        These resources are widely available in bookstores and various places on the internet.