What is the theme in A Man Named Dave: A Story of Triumph and Forgiveness by Dave Pelzer?

Forgiveness is at the heart of this story. As the subtitle suggests, David Pelzer's adulthood involves his forgiveness towards his mother. Shortly after he publishes his first two books, about his childhood, he warns his son that refusing forgiveness hurts one's self, not the person one refuses to forgive. Pelzer believes in order to have a peaceful life, one must achieve forgiveness, even for the most hurtful events.