Yoga students occasionally ask me what books would help them with their understanding of Iyengar Yoga.
Here are the four books I would recommend first:
The books Light on Yoga and Yoga: The Iyengar Way (the first and the third books shown above) are the first two books that I bought, on the recommendation of my first yoga teacher, and I continue to refer to them.
Light on Yoga, by B.K.S. Iyengar, is considered the "Bible of Modern Yoga". It was first published in 1966, and continues to be one of the best references for studying and practicing yoga, including sections on philosophy as well as yoga asanas (poses) and pranayamas (breathing exercises). If you're an experienced Iyengar Yoga student, you'll notice that some of the poses look a little different than how we typically teach them now, and there are very few props that are used. It's interesting to see the progression in what the Iyengars think is important in our practice of the yoga poses. It's not a static subject.
Yoga: The Iyengar Way, by Silva, Mira, and Shyam Mehta, has large, clear photographs of about 100 yoga poses, and detailed instructions for how to do the poses, what to pay attention to, and tips and variations for how to practice. There's a section on yoga philosophy, and a practice sequence section in the back.
How to Use Yoga, by Mira Mehta, is geared a little more toward the beginning level yoga student compared with Yoga: The Iyengar Way. It has step-by-step instructions, shown in clear photos, of how to do the yoga poses, including correct prop usage.
The Tree of Yoga, by B.K.S. Iyengar, is the best introduction to yoga philosophy that I've come across. In this book, Iyengar writes about yoga and how we live our lives; the different elements of yoga (the Tree of Yoga); yoga and health; and yoga and spiritual growth.
Read 10 Best Iyengar Yoga Books for more recommendations.