In The Kite Runner by Khaled Hosseini, what lesson can be learned from Amir's change throughout the novel?

There are many lessons to be learned from Hosseini's The Kite Runner. Perhaps the most powerful one is that we can overcome the scars and shortcomings of our upbringing to become good and happy people.  As the book opens, Amir is in a conversation with his old family friend, Rahim Khan, who offers him an opportunity to be a better person, to redeem himself from his wrongdoings.  Beginning the book this way, the author is probably letting us know what is to him the book's most important lesson.

Amir's childhood, in spite of his being raised in the lap of luxury, is far from idyllic in many ways. He lives in a culture in which there is a great deal of ethnic and religious prejudice, which affects his relationship with Hassan, who is a Shi'a Hazara, allowing Amir to consider Hassan and his father Ali beneath him. Amir has qualities and talents that his father, Baba, does not appreciate or value, a gift for storytelling and writing and a love of reading.  In fact, Baba considers Amir to be unmanly, which is apparent when Baba sits him down for a talk about sin and says, "I mean to speak to you man to man. Do you think you can handle that for once?" (17). Amir's relationship with Baba has undercurrents that cause Amir to be envious and even cowardly, as he senses some competition with Hassan for Baba's attention and affection.  He is unaware for many years that Hassan is Baba's son, too.  Amir's actions cause harm to Hassan and Ali that is irrevocable, and he carries the weight of guilt for them.  Added to this is having to flee to America, leaving a life of comfort and wealth behind to be lowly immigrants in a new and alien culture.  Amir's start in life is not the easiest.

In the new world, though, he begins to grow as a person, gaining a new appreciation for Baba and earning his respect.  He learns to navigate America, gains the courage to court Soraya, begins his writing career, and helps his father.  When he gets the call from Rahim Kahn, offering him "a way to be good again" (2), he has grown enough as a person to heed the call.  His mission in Afghanistan is to rescue Sohrab, the offspring of Hassan, who is now gone, from the hands of his old nemesis, Assef. He must overcome the resentments of his childhood, the scars of feeling himself to be an unloved child, and the cowardice and prejudices that had made him such a poor friend to Hassan.  In short, he is becoming a mature young man who now has the inner resources to vanquish the enemies within and without. 

That Amir is successful in his mission is a testament to the idea that we can get over our own childhoods and take responsibility as the people we want to be.  The playing field is seldom completely even as we begin our lives, but it is up to us to make the best that we can of what we are given.