Yeah, I made a separate comment, but AudioBookshelf can play nicely with ebooks and comics. It’s not super smooth, but provides the most features in a self hosted solution from what I’ve tried.

I just use AudioBookshelf for books. It’s a little annoying, but basically just requires an extra nested folder structure.

The best part is offline reading seems to resync back to the server, so you can download books for local reading or read through an internet connection.