What is the theme in The House of God by Samuel Shem?

Coming of age as a physician is the main theme of the story. While Roy is an adult, he is coming of age in the world of medicine. He starts out anxious and afraid of what he's facing and he doesn't know much about the world of medicine, despite his earlier training. He comes to learn a lot of unorthodox ways of dealing with patients and learns the rules of the House of God. He learns through dealing with patients and through the Fat Man, who gives him pearls of wisdom along the way.