This thought arose when I tried to go to a site with fan fiction, but it was blocked.
The difference from Lemmy is that after clicking on a post with the cover and description of the book, a topic with the first chapter of the book will open (just like on sites for reading books online).
Also useful will be a button where the author can insert a link to the epub file (from the list of allowed file exchangers). And tag support.
Unfortunately I don’t have programming skills, so this is just an idea.
If you build it, they will come.