calibre-themes
This is a repo where I'll dump my Calibre reader themes. I like to have a few options, so I'll post whatever alternatives I come up with.
To use, just copy the contents of any of the css files into your calibre
ebook viewer settings. Just open up an ebook, click preferences, then
the user stylesheet tab. Paste in the contents of the file. Then, just
save and admire how cool you are.