theme of novel kite runner

There are quite a few themes that you can consider. I I think that guilt and living with guilt is important:

Amir is rescued by some neighborhood bullies by Hassan, a boy who holds the role of servant in his household. Later, when Hassan is being attacked by these same bullies, Amir stands by and allows it to happen. That moment drives the guilt he lives with the rest of his life but also expands the guilt he feels for other actions before and after this event. Amir says that Hassan’s devotion to him is complete and unwavering but that he only plays with Hassan when the wealthy children of his father’s friends aren’t available. It seems that Amir looks back at his childhood through a haze of guilt that actually stems from Amir’s decision to stand by while Hassan is attacked. Amir might have lived with this guilt for the rest of his life if not for Rahim Khan who realized that Amir needed desperately to find a way to atone for that guilt in order to find peace.