They say it can increase your productivity, and hot damn does that man need it. LLMs work best when manipulating input text along with contextual content. That sounds almost exactly like partially-edited manuscript and conceptual thought doodles plus several existing storyline books.
Admit it, if he dies before finishing, and someone publishes the result of such an AI output, you would read it. So he might as well get some AI help to finish it “himself”, sooner, right?
I don’t think an LLM is going to help him in untangling the sprawling storyline he’s got. Besides I read authors for their vision not some synthesised average of their previous stories.