I get that an llm can be a useful search tool over internet, but stories? Why? If someone is going to spend 5+ hours on the contents it better be made by a human.
You are actively doing a disservice to humanity by eroding trust in writing
I like reading. I dedicate a good amount of my time to reading. I find it quite a personal experience to read an author's work. They have put far more time into the book than it takes me to read it, it feels like their thoughts and ideas have been carefully distilled down. The Mark Twain quote about writing a shorter letter, I think is a good analogy - with some books I can feel the care that was taken to respect the reader's time.
This use of AI is the opposite. I find it repulsive and disrespectful to the reader. I don't want to read a hundred pages of slop. The same negative sentiment as many people feel towards AI art and music.
I don't mind if an author asks an LLM to rephrase a sentence or touch-up grammar, but I would never want to read a generated book like this.
Allow the user to provide an arbitrarily-detailed outline, chapter by chapter, with characters, situations, dialog, emotions,... - everything that could be an ingredient in a book "recipe".
And I wouldn't package it into a completed book just yet - instead, provide a formatted manuscript (which you already do) which is open for revisions and rewrites, before inserting it back into the pipeline for final packaging.
What you have here is a high-level concept with premature pricing options. I would withdraw it, and keep developing it into something which offers unprecedented assistance in novel writing.
Oh, and at the very least, provide an example of the finished product, so users know what they're paying for!