That's possible. The quality is certainly not going to win any prize.
It is because either:
1. It is riding over the success of best-seller and mislead the potential buyer into thinking it's related to the original -- in which case the problem isn't quality of the output, but legality of the advertizement and it should certainly be removed.
2. It is... bad but good enough for buyers. Much like the million or so listening to AI generated music or Lady Gaga instead of Bach.
Is it great? No. Is the market a good indicator of greatness? No, if we go with Van Gogh never selling a single work. It might be satisfying enough for the low price and thus meeting the need of people (reading low quality "companion" books that sound like fan-fiction). And if it satisfies the public, it is not slop. It might not meet your stringent standard, but if it is good enough for people who buy it, it can't be called slop. It is consumer-level.
Much like with images. Do image model produce great works of art? Certainly not. Do we need Jeff Koons to design our online RPG tokens? Certainly not either. They do consumer-level result, which meet the need of the consumer. If artists are losing commissions right now, it is because AI doesn't produce slop the customers don't want, it's because it is producing a satisfying result. Certainly not perfect, but enough to fill the need.
Of course, I can see how one could call consumer-level anything slop, but that's elititist, I think, or a binary fallacy. You can have average-quality products that consumers will enjoy (a burger joint, for example) without it gaining Michelin stars. I wouldn't call the burger joint slop, even if it only satisfies its customers.