What is the theme in Autobiography of a Yogi by Paramahansa Yogananda?

The Self-realization Fellowship is Yogananda's offering to humanity in the hope that we may all know ourselves as clearly and deeply as he did. He felt that when we understand the true nature of our existence, we will no longer make war among ourselves, but will live in the peace that was intended for us. Self-knowledge, in this respect, comes from understanding the scientific fact that there is no such thing as material stuff, and that everything is made up of energy and light.