I think this is happening because I built against a newer version of glibc. Very sorry about this. I will try to get a Flatpak out as soon as I can. Btw, what screenshot tool are you using? Love the transparency.

I have a feeling this will be a heavily requested feature. So there is a chance :)

No. PDF is currently out of scope. The app is built around EpubJS and is really more designed for responsive book formats. Including PDF support would mean incorporating something like pdf.js and would require tons of effort and rewrite which is off course at this moment.

Plain text files are also not supported currently, But this can be included for the 1.0 release. Thanks!

Thank you so much. I would be open to renaming it and even taking suggestions in the future.