The Kite Runner book by Khaled Hosseini

One frosty day in the winter of 1975, Afghan boy Amir witnesses a terrible act. This event forever changes both his own life and the fate of his close friend Hassan. But the thing is not only in what he saw, but also in the fact that Amir did not intervene, did nothing, stood aside. Cowardice, even apostasy, will haunt him throughout his life, first in Afghanistan, then in America, until Amir musters up the courage, challenges all his inner demons and finds "a way to be good again."

The Kite Runner is the debut novel by Afghan-American author Khaled Gosseini, published in 2003 and subsequently topped The New York Times bestseller list for two consecutive years, and in 2007 a film of the same name was made based on it.