Backstory: I've always been fascinated by choose your own adventure books. I'm not creative enough to write one myself but maybe I could write part of one.
The Idea: A crowdsourced choose your own adventure book.
Deep Dive: You would have to seed/start each story with a few paragraphs, users would be able to submit parts of the story but only after they rate the other options. Every time someone rates different parts of the story, the lower rated ones drop off, eventually leaving only a few options and a complete story.
You would have to refine the process but the idea is to have groups of people write a choose your own adventure type book that would be published and those with chosen parts of the story receive a percent of sales.
Validation: Interactive choose your own adventure stories are fun!
Monetization: You would take a cut of each book sale and distribute the rest to the contributors.