Who is Junior?

In Sherman Alexie's young adult novel, Junior is Arnold Spirit Junior, a fourteen-year-old Native American living on the  Spokane Indian Reservation in Washington. He has some physical challenges from being born with hydrocephalus.  Junior's family is poor, and he is very intelligent.  He likes to draw cartoons and play basketball. 
Junior tells the story from his perspective, so he is the narrator and the cartoonist, as the novel is his diary.  His youth and inexperience make his perspective as the narrator sometimes unreliable because he is not yet fully self-aware. 
Junior does not feel completely at home on the reservation, and when he transfers to an all-white school about twenty miles away, he does not feel entirely at home there, either.  He is caught between two cultures and is ultimately able to find some acceptance in both.