Any way to detect if dark theme is active in iBooks from within EPUB?

Question

Does iBooks add something like a CSS class or anything else in order to be able to style some sections of the book differently (in lighter colors) when the night mode is active?

Answer 1

iBooks adds a __ibooks_internal_theme attribute to the :root (html) element with a value that's changing with the theme selected.

Go ahead with this:

:root[__ibooks_internal_theme*="Sepia"]    
:root[__ibooks_internal_theme*="Night"]

You can find more details on GitHub: theme-detect.css

I will eventually add details on CSS limitations for the three themes.