Having written one full fiction book and ~70% of another in the past 1.5 years of the “reasoning” AI era, one thing is abundantly clear to me: AI is dreadful, cringe even, at writing creative fiction even with the most elaborate prompts – I haven’t used a shred of what it’s given me. That includes Opus 4.6.
However it is exceptionally good (and getting better, especially Opus) at editing – developmental, line, and copy. This has been invaluable for me in the writing process.