It doesn't, that's the whole point. You can produce output that passes the smell test with naive buyers in a matter of hours. If you want to write good LLM books, then you gotta work closer to human speed - weeks, months - which allows others to produce 100 slop-books in the same timeframe. You still lose.
If an author let AI do 90 to 95% of the work, cleaned up the remaining 5 to 10% themselves, would you say AI or the author wrote it? Because this is roughly the split between an author and an editor, with human writing, now.
The work is either: (1) the act of concealment: generating an AI book that cannot be detected as AI generated; or (2) actually just writing the book yourself.