At a normal walking pace, it would take around 20 minutes to walk around the 27-acre square field. If the 27 acres are in any shape more rectangular or irregular than a square, it will take longer to walk around.
Hosseni wrote The Kite Runner to show the world the way that common issues of identity, assimilation and power are carried out in his culture in Afghanistan. He spends a great deal of time developing Amir and showing how he comes to a self-identity by the end of the book.
All of the novel's main characters, like real humans, live their present lives in specific ways because of their past. Amir--The novel is based upon Amir's view of his past action--betraying Hassan--and we wouldn't have the main plot without Amir's... The universal theme of The Kite Runner is, of course, redemption.