[doodliego]

I've created 80+ ebooks using Calibre, but it's too over-featured for casual ebook reading. I've used IceCream for that but I'll give Bookworm a look.

[themodelplumber]

That's a lot of ebooks. Do you write for a living?

[starks1de]

Mupdf ( https://mupdf.com ) also supports ePub. I personally using it with zathura for vi keybindings and theme support ( https://pwmt.org/projects/zathura-pdf-mupdf )