How does Amir change throughout the book?

As a young boy Amir witnesses a crime of rape and assult againts Hassan.  He runs away in terror and spends the rest of his life feeling guilty because he does nothing to help Hassan during or after the incident.

"As a boy, Amir is bookish, thoughtful, and nonathletic. An introverted thinker, he prefers to write stories in his notebook rather than play soccer."

As a man Amir struggles with the inner conflict of his decisions of childhood.  He eventually has the opportunity to return to his home in Afghanistan and redeem himself.  Although it is too late to help repair his relationship with Hassan, he can help Hassan's son, Sohrab.  Amir grows to understand himself; he grows into a man of bravery and insightfullness.