•Why it earns a slot
Why it earns a slot: it turns the entire Arthurian legend into a controlled experiment on how an ideal collapses once the people enacting it turn out to be merely human.
Twelve books of blank verse take Camelot from Arthur marrying a woman who never noticed him to a king carried off in a barge, wondering aloud whether he is even dead.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.