I was in a related space, self-publishing of books. And it's very strong. There is a huge, huge audience of frustrated authors out there. People who have journals or stories or novels they want to publish for the world to see but the big book publishers won't go near. The big publishers focus on the Harry Potters and big titles that drive the industry and pay the bills.
You should obviously do more research because I'm not really answering your question with any specifics but it's an exciting space.