I'll start: it became my notes app, because I can have insights on the notes I'm taking. Not an ideal use case, but it is fun for side projects ideas.
Example, I was fiddling with a PGN project idea while waiting for the Christmas dinner: https://chat.openai.com/share/eb975eaa-1c37-413f-a6a0-b17eb2f1bdf3
* A story bible (asking questions about characters, timelines, plot points, etc that I might have forgotten)
* A brainstorming tool that uses existing themes and characters for new ideas
* A rudimentary developmental editor or critic (does not replace my human dev editor, however)
* A character and environment art generator (this one is hit and miss with characters especially)
Tip for anyone doing this: make a separate GPT for each series. When I tried to upload books in two distinct series, even clearly labelled in the data, it started getting them confused. Works better to split them up.