Recently I wanted an audiobook version of a book I was going to read, but it didn't exist. I put this together using Coqui-TTS and the voice sounds really good. It's not as good as Eleven Labs, but it's far better than anything else I had previously heard.
https://github.com/aedocw/epub2tts
If anyone knows of better TTS synthesizers that I could use please let me know!