While this is fiction, it feels like a comedian's autobiography. It's chatty, and the narrator regularly pokes fun of himself and the situations he finds himself in. Incredibly authentic feeling. The author clearly knows what life is like on a reservation - whether through research or experience (I didn't look up his history to check).
Very similar in feel to Trevor Noah's Born a Crime (except that that book actually is an autobiography - and if you haven't read it yet, you should), Absolutely True Diary tackles issues of racism, poverty and culture clash in a very accessible and lighthearted way without diminishing their importance.