I've been using Readest (https://web.readest.com/) but I'll definitely be checking this out.
I'm a fan of audiobookshelf. Don't let the name fool you, it does a lot! I use it for podcasts, audio books, & ebooks. It's great!
For someone looking for a bit more than this, I recently got Bookorbit running and its quite powerful for being so young. https://bookorbit.app/
If it is helpful to other people here is how I manage my ebook library with flatfiles and heterogeneous devices (Android, macOS, iOS, Kindle, etc)
I have my own eBook library hosted with copyparty. It is a single binary. Runs on plain files. And speaks OPDS for integration with KOreader (Kindle) or Readest (iOS/macOS). https://github.com/9001/copyparty#opds-feeds
It also speaks webdav so I can quickly sync everything via rclone to an SD card on devices like an Android tablet.
I really like the convenience of flat files and multiple protocols.