Now, I understand that "Iyengar: the book" is different from "Iyengar: the class." In classes, Iyengar is famous for his energy and fierceness, even going so far as to strike students to (as he has it) stop them from making mistakes that could injure them. Certainly he has been successful- his strenuous and highly precise style of yoga is now taught around the world and he stands as possibly the world's foremost practitioner of the art. His more recent books (Light on Yoga was first published in 1966) find him introducing props such as blocks to help beginning students properly align their bodies while not stretching as far as advanced students, and expounding at greater length about the spiritual foundations of his art. His life's goal has been to help people achieve enlightenment by joining the mind to the body ("yoga" comes from the Sanskrit for "to yoke"), and the physical efforts are, in reality, secondary to the inner journey students undertake. In fact, the first section of Light on Yoga, the part without helpful pictures and such, is really more important to Iyengar's presentation than all the twisty acrobatics. That was something that, for all my serious aspirations and meditation, never sank in.

A former student of Iyengar explains the difference well. In the introduction to his book Yoga, The Spirit and Practice of Moving Into Stillness, Erich Schiffman writes,

"His methodology worked. Many people attempt to discredit him by saying his yoga is not spiritual. But here it was! Spiritual in the most practical, grounded, obvious way. And it was equally obvious from what he said to me that his intent all along was to impart the experience of yoga - not just put everyone through the paces, physically speaking. The whole point of this physical, hard work - and it was very physical and very demanding - was to get into a deep meditative state. . . .

It took me a while before I was able to describe what had happened, but as I look back, I can see that this is when yoga finally became mine. I "got" yoga....

In Iyengar's classes, for example, he would say "Move your little finger this way " or "Stretch the skin here" - and I would, and it always felt right.... But I had no idea where he was coming up with all this marvelous information, this detailed insight into how the poses worked. But when [a colleague] taught me to create a line of energy [e.g. down my arm], suddenly all the intricacies that Iyengar had been talking about began happening by themselves.