•Why it earns a slot
Why it earns a slot: it invented the modern psychological thriller by making the crime the opening chapter instead of the twist, then spending five hundred pages on the mind that cannot live with what it already did.
A broke ex-student talks himself into murdering a pawnbroker with an axe, then spends the rest of the book failing to outrun what he did.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.