It's a tonal spoiler, I guess you could say. It mostly spoils whether the book ends on an upbeat or dim note, although I guess there's also some vague detail as

It's a tonal spoiler, I guess you could say. It mostly spoils whether the book ends on an upbeat or dim note, although I guess there's also some vague detail as to a large event that results in this ending. I read the paragraph and still want to read the book.