I listened to a few samples, too, and my impression is the same: a few sound AI-ish in spots, but often I would not be able to tell that the reader wasn't human

I listened to a few samples, too, and my impression is the same: a few sound AI-ish in spots, but often I would not be able to tell that the reader wasn't human. I’ve heard better human-read audiobooks, but I’ve also heard worse. Most of the books identified as “Apple Books audiobook narrated by a digital voice based on a human narrator” seem to be romance fiction. From what I’ve read about the genre, romance novels are written in huge quantities based on standard story, character, and situation templates, and enthusiastic fans often read dozens or hundreds of the books a year. Romance-fiction audiobooks would therefore seem to be a prime target for good-enough AI production. Presumably the stories themselves will be next.