Hey all,
I've built a google home app which plays all librivox books (>15k) directly on google home and all devices that run google assistant, which includes most phones, tablets, google next devices and speakers like sonos.
The app is called 'Book Reader'. You can try it via this link directly:
https://assistant.google.com/service...00009e67666043
The details of the app are at
https://blog.speakhub.io/free-audio-books
A recommendation list to get started is here:
https://blog.speakhub.io/recommended-audio-books/
Hope its useful for you and happy for feedback.