Hosseini explores many themes in The Kite Runner, including those found in eNotes' TKR/Themes 

• Identity and Self-Discovery
• Family and Fatherhood
• Journey and Quest
• Heritage and Ancestry
• Assimilation and Acculturation
• Abuse of Power

but for me, the primary theme is that of Redemption, Atonement and Salvation. From the very first chapter, in which Rahim Khan assures Amir that There is a way to be good again, the novel's characters battle their guilty consciences over their past actions. Amir has the heaviest burden, finding a way to forget the sins he has committed against Hassan. He begins a new life in America, but even the thousands of miles between California and Kabul cannot erase his past. He becomes an insomniac and, when he sleeps, terrible nightmares remind him of his misdeeds against Hassan. Even Baba's death cannot erase the memories, and it is only after Amir learns about his family's terrible secrets from Rahim does he understand the meaning of Rahim's promise. If Amir can find Sohrab in Taliban-held Afghanistan, perhaps he will be able to forgive himself. The beating he takes from Assef goes a long way toward self-atonement.

My body was broken--just how badly I wouldn't find out until later--but I felt healed. Healed at last.  (Chapter 22)

Baba has a secret that Amir does not discover until after his father's death. Baba's philanthropic endeavors in Afghanistan were no doubt fathered by the guilt of Hassan's true heritage, and Baba faithfully dotes on his remaining son during his final years in California. He takes his secret to the grave, further infuriating Amir, who uses his anger to garner the courage to return to Kabul in search of Sohrab.

He [Hassan] was gone now, but a little part of him lived on. It was in Kabul.
     Waiting.  (Chapter 18)

Sohrab, too, seeks salvation in California, and their is a "melting" of the icy relationship between he and his uncle at the end of the story. And even Soraya finds a way to make up for her past transgressions. She learns to stand up to her father, becomes a teacher instead of a lawyer or doctor, and accepts Sohrab into her household.

In the novel The Kite Runner by Khaled Hosseini, what are some main themes that the author explores throughout the story? 

Two themes of the novel are the search for identity and the importance of sacrifice. Throughout the book the narrator and central character Amir struggles to understand and come to terms with himself, especially after an act of cowardice in his youth. In this act he watched the bully Assef beat and rape his lower-class friend Hassan. Amir does not intervene to help his friend and will not tell his father what happened, thus projecting a false identity, as he fears his father will despise him for cowardice. Amir is racked by guilt over having failed Hassan. Amid all this inner turmoil, he continues to grow up and must try to come to terms with himself. This search for identity is aggravated when the Soviet invasion forces him to flee to the United States. Much of his identity was family and community based and now that foundation has been ripped away—but this also acts as a gift that offers him a new beginning.

Sacrifice is symbolized by the way the kite runners rip their fingers cutting the kites from the sky with glass-embedded string. The young Amir is proud to cut his fingers to show his father his kite-fighting ability. Later, trying to redeem himself, Amir sacrifices to rescue his half nephew. Bringing the novel full circle, the adult Amir near the end will again cut his fingers flying a kite to try to bring life and hope back to this depressed half nephew. Also at the end Amir is willing to make sacrifices to save Hassan's son.

In the novel The Kite Runner by Khaled Hosseini, what are some main themes that the author explores throughout the story? 

Throughout the novel The Kite Runner, Khaled Hosseini explores several themes which include relationships among family members, redemption, and violence. The dynamics among family members are examined throughout the novel, in particular, Amir and Baba's father-son relationship. Amir seeks to gain his father's admiration as a child, while Baba takes his anger out on Amir because he himself is unable to openly claim Hassan as his son without incurring social repercussions. The importance of family in the Afghan community in America is significant and is portrayed when Amir marries Soraya. Ali, Hassan, and Sohrab's adoptions are also important, and the relationships among their family members are explored throughout the story.

Hosseini also explores the theme of redemption throughout his novel. Amir's personal journey to find redemption to atone for his past sins is the driving force behind his decision to rescue and adopt Sohrab. Hosseini suggests that only through personal sacrifice can one find redemption.

The theme of violence is also prevalent throughout the novel. Hassan's rape is a significant moment in the novel and the emotional toll it takes on the characters impacts their lives. Hosseini also depicts the destructive nature of violence by illustrating the damage done to Afghanistan. Characters not only suffer from violence, but its cyclical nature negatively impacts future generations.