Hi @Delucag, thank you for reaching out to the Sonos community. I appreciate you for bringing this concern to us. Let me help you out with this.

Playing audiobooks from Apple Books is not available yet in Sonos. What I can do is send in a feature request to make this available in the Sonos app. We don't have the timeline and the information yet to share with you about this but you can check our announcements here in the community or from our website.

You may check out for the available music services that you can add to Sonos and play audiobook or you can reach out to Apple support to further assist you on this.

If you have any questions about this. We and the community are always here to help.

Thank you for the timely and clear response.

Hi @Delucag, thank you for your response.

Please do not hesitate to reach back to us or create a topic if you still have further questions or concerns. 

The Sonos Community is always here to help.

I would appreciate Apple Books being added as I am sure many others would. 
I have a large collection of audio books on this platform and listening to these through the Sonos app would work really well. 

I certainly agree. However, it isn’t up to Sonos to make this happen, it is a choice made by Apple. You should lobby them.