It's a very indepth novel about an aspect of modern Native American spirituality--called sorcery rather than shamanism in this book--that is rarely seen and explored. It is extremely philosophical, helps you look at the world in a completely different way, reads like a fantasy novel, and is told from the point of view of a Western student studying under Don Juan, a Native American teacher of this way of life.
You can read it either as pure fantasy, or, for those who believe in magic and a magical world, as a fantastic account of a magical journey.