I have a sci-fi series I've followed religiously for probably 10 years now. It's called the 'Undying Mercenaries' series. The author is prolific, like he's been putting out a book in this series every 6 months since 2011. I'm sure he has used ghost writers in the past, but the books were always generally a good time.

Last year though I purchased the next book in the series and I am 99% sure it was AI generated. None of the characters behaved consistently, there was a ton of random lewd scenes involving characters from books past. There were paragraphs and paragraphs of purple prose describing the scene but not actually saying anything. It was just so unlike every other book in the series. It was like someone just pasted all the previous books into an LLM and pushed the go button.

I was so shocked and disappointing that I paid good money for some AI slop I've stopped following the author entirely. It was a real eye opener for me. I used to enjoy just taking a chance on a new book because the fact that it made it through publishing at least implied some minimum quality standard, but now I'm really picky about what books I pick up because the quality floor is so much lower than in the past.