•Why it earns a slot
Why it earns a slot: it is the 1798 pamphlet where two poets deliberately traded classical diction for plain speech, and that decision is still the working definition of modern poetry.
Two young poets publish anonymously, betting that a cursed sailor's ghost story and a girl who refuses to subtract her dead siblings can prove ordinary speech is enough for poetry.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.