Yes, I'm now using KOreader for reading epub/texts and Tachiyomi for manga.

Epub format is currently the most popular out there (I have all my books stored in that format too). I do hope they fix their reader to handle epubs properly or even add some other format support like cbz in their next big update that's coming in november but I doubt it.

Anyway, I already got used to alternatives. I probably won't go back to reading with the default app.