I tried it a few months ago to narrate an epub in Apple Books and it was very broken in a weird way. It starts out decent but after a few pages, it starts slurring, skipping words, trailing off not finishing sentences and then goes silent.

(I've just tried it again without seeing that issue within a few pages)

> Siri voice or some older voices

You can choose "Enhanced" and "Premium" versions of voices which are larger and sound nice and modern to me. The "Serena Premium" voice I was using is over 200Mb and far better that this Show HN. It's very natural but kind of ruined by diabolical pronunciation of anything slightly non-standard which sadly seems to cover everything I read e.g. people/place names, technical/scientific terms or any neologisms in scifi/fantasy.

It's so wildly incomprehensible for e.g. Tibetan names in a mountaineering book, that you have to check the text. If the word being butchered is frequently repeated e.g. main character’s name, then it's just too painful to use.