•Why it earns a slot
Why it earns a slot: it hands its moral climax to a barely literate boy who chooses hell over turning in his friend, and the book never once tells you that's the point.
A boy fakes his own murder to escape his drunk father, then risks his soul on the Mississippi to keep a runaway friend free.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.