Ideally a reader app that's shipped in the default F-Droid repo, or can be installed and updated with Obtainium. But for a really good mobile reading experience, I'd compile from source if I had to.
Does anyone know of a good reader app for Android?
One that allows me to scan my storage for files of text (in a range of formats, .TXT, .PDF etc), add them to an in-app library, and open them for reading from there. And when I open unscanned files from storage, for reading, it asks me if I want it added to the library. And allows me to scroll down from page to page. Not "turn" them horizontally.