Authors, including Hosseini, often use literary devices to support the plot of a novel. The term "support" is an important one because it means that the literary devices provide assistance to events in the novel and are not themselves the events in the novel. The following are examples from The Kite Runner: 

Imagery: Evoking all the senses

People often make a mistake and assume that imagery refers to descriptions that only appeal to sight. However, imagery is meant to appeal to all senses, and Hosseini uses such holistic imagery to draw the reader into the scene and empathize completely with Amir. Rather than observing Amir, we experience things with Amir, hearing and smelling and tasting and feeling and seeing everything that he does. This helps to develop the plot by investing the reader more fully into its progression. 

Symbolism: The Kite

Kites are a recurring symbol for Amir's childhood and his relationship with Hassan. The novel in fact opens with Amir glancing up and seeing "a pair of kites, red with long blue tails" immediately after a prominent figure from his childhood, Rahim Khan, telephones (2). Kites play a key role in the traumatizing assault that Amir witnesses and then guiltily carries for the rest through to his adulthood. Kites again are present at the end of the novel when Amir has atoned for his sins against Hassan and is cultivating a happier childhood for Hassan's son, Sohrab. In this final scene, Amir asks to "run that kite" for Sohrab, thereby fully completing the circle of his childhood and adopting Hassan's role as caretaker for his son (327). 

Dreams: Characterization

Hosseini uses dreams to better develop the characters in his novels, making them more complex and allowing the reader to understand the motivations behind their various actions. This development also allows the reader to hypothesize about characters' actions, prompting investment in the progression of the plot.