The Absolutely True Diary of a Part-Time Indian
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As a "diary" the story is told (very authentically and with much self-deprecation) in Arnold's 14-year-old voice. He never shies away from who he is or what he's thinking or feeling, just puts everything out there. He also draws as a way to vent, so the book is littered with scraps of cartoons whose humor ranges from witty to ruminative to quite dark. And the cartoons don't just restate what's in the text, they add a lot and help define Arnold's mood and express his feelings.
Although this is ostensibly a young adult novel, I can't imagine anyone of any age it wouldn't appeal to. It's heartwarming and heartbreaking, hilarious and tragic, and I absolutely loved it from start to finish.