I'm arrogant enough to think that books are not going to teach me about life -- just about this particular author's view of life. His view is no more or less valid than my own.
For example, one theme in the book is the pull of the "old country" for an immigrant. The author is trying to teach us that a person cannot leave behind his old identity and become something new -- Amir remains strongly tied to his Afghan past.
But this does not ring true for me, or at least not in all cases. My own father is an immigrant who has become thoroughly Americanized. He spends a lot of time thinking about whether he would have been different if he had stayed in the "old country," but he does not feel any compulsion to return to his old ways.
So I learned some things about how the author sees the world (like this thing about immigrants) but I do not believe I learned any "truths" about life.
This is a great question as this novel is one of those books that does encourage us to reflect critically on our own lives and hopefully come out of reading the book as a better person. However, for me, I think the novel says a lot about the need to acknowledge and face up to your mistakes and do what you need to do to make them right. This is what Amir does by returning to Afghanistan and adopting the soon of Hassan.
I think that the aspect of identity revealed through the work is probably what resonates the most. Amir leave Afghanistan and lives in America, and seemingly, exists devoid of his past. Yet, through events that were almost preordained, he is forced to acknowledge his past and embrace it. This is seen when he goes back, his revelation about his Hassan being his half brother, and in pursuit of Sohrab. Amir's years of study in America as well as his assimilation into American culture did not allow him to escape from his identity and the moral and ethical obligation that accompanied it. While he might have been silent when Hassan was attacked, Amir cannot remain silent when he recognizes his nephew is in danger. His prayer to God in the hopes of saving Sohrab is another example of this. He could not stray from his faith, something that had been dormant for years. Yet, in a moment of crisis, a stunning instant of anguish, he turns to his religious identity. The notion of identity is something that is shown to be fluid "a thousand times over" in the novel, something that proved to be quite meaningful for me.
The kite runner taught me to appreciate people around me who try their best to help me out in ever way possible. it taught me to be like hassan to stand up for a friend when he is in need. It taught me that life can be full of misunderstandings and we can fix them or try our best to. it taught me to own up to my mistakes ans stand up for what is right.