Doesnt directly answer the question, but nowadays there are good and free TTS that will essentially turn your entire ebook to an audiobook. (Elevenlabs Reader for example)
Doesn't directly relate to your comment, But I hate ElevenLabs for purchasing Omnivore and shutting it down.
Same way I feel about HP for doing the same to Palm
I like these tools for content where no narration exists (especially for proofreading my own writing) but they aren't anywhere near as good as a good human narrator. e.g: https://youtu.be/LPZrReZ5H9Q?t=103