It won't be a sudden thing. The socially necessary labour time for a novel will drop precipitously and mysteriously for a while until it comes out that a whole bunch of stuff is partially written by GPT-3 and partially by a human. Fully handwritten works will become an idiosyncrasy, and will take on a character of their own, a collection of William Morris types still slavering over every syllable.

Is it good or bad? Depends on if the automation frees people or renders them redundant.