I use an app called ReadEra which I like very much. I use the free version but it looks like the premium version does what you're looking for: it can sync via Google drive and you can upload your own fonts. (Premium is a one-time $20 payment, not a subscription.)
I don't think Android really has one anymore you can sync bookmarks and stuff but for the library you'd probably need to keep it in the cloud.
I do remember an Ebook reader that did do this very well called fabrik or something similar but it vanished from the store about 6 months later with no explanation (really annoyed me as I'd bought it).
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Best ereader app that will sync libraries across devices, both iOS and Android, and lets me choose any font? | Spyke
Have you tried BookFusion? I sync my Calibre library to it and use it on iOS and my android ereaders. Just checked and it has Open Dyslexic.
Does it work offline?
Yes, after you download a book to your device.
This app, if it existed, would cause a war.
If it’s a full blown hot class war in the US, I’m in
I use an app called ReadEra which I like very much. I use the free version but it looks like the premium version does what you're looking for: it can sync via Google drive and you can upload your own fonts. (Premium is a one-time $20 payment, not a subscription.)
https://readera.org/
I used to use Moon+ Reader with the Dropbox integration.
I don't think Android really has one anymore you can sync bookmarks and stuff but for the library you'd probably need to keep it in the cloud.
I do remember an Ebook reader that did do this very well called fabrik or something similar but it vanished from the store about 6 months later with no explanation (really annoyed me as I'd bought it).