This is a workflow problem.
What the LLM normally needs:
- very basic outline: what the story is about
- basic cast of characters: like fiction/plays of the 18-1900s
Then you go chapter-by-chapter. But the most critical thing is that you MUST provide the chapter beats. From start to end. Location, environment, events, any critical conversations. For a chapter that is 2-3K words, this chapter outline often becomes 2-400 words or more. Because you have the story in your head, you can handle the stuff that the LLM is likely to screw up.
There are ways to build a system where the LLM can keep track of many things, but then that becomes programming, which is just as boring.