The Adventures of Huckleberry Finn
Twain skewers the pretension and hypocrisy of "a god-fearing Christian" nation that enslaves 4 million African Americans. Huck, with his child's common sense, sees through the hypocrisy and exposes us to the materialistic, selfish, and immmoral realities beneath the Christian pieties and middle-class "proprieties." The moment where Huck decides, against everything he's been taught to believe, that "Nigger Jim" is a human being as much as Huck, is the greatest moment in American literature. In recognizing Jim's humanity, Huck decides break the law and NOT turn Jim into the authorities, who would re-enslave him. Huck realizes that doing the morally RIGHT thing may mean breaking the law. Every American should read this important (and did I mention it's hilarious?) novel.