Backstory: I was chatting the other day with a friend about those "choose your adventure" games we read as a kid. I got to thinking it would be great to bring that idea to modern times.
The Idea: A digital version of choose your own adventure.
Deep Dive: You would create a digital story with multiple endings and display it to users, giving them choices along the way to help guide the story in the direction of their choosing.
You could make this a social game where users can see the path their friends have taken as well.
Validation: These books were huge when I was a kid.
Monetization: You could charge a monthly service for access to all "books" or charge on a per "book" basis.