What is the best book reader? I am looking for the reader with dark themes support.
Evince is good, but it has only a Night mode and no themes.

    Solarmass I like the E-Book Viewer application that comes with Calibre. It appears to have dark theme support as well.

    I've also used Bookworm and Foliate (flatpak), which have dark themes as well. I don't use them regularly, but did try them in a pinch when Calibre briefly had some issues.