Want to highlight text and take notes… No problem, Foliate can do that.
Want to use your favorite system font? You can do that. Remarkably it works very well. I’ve been using eBook readers for over ten years now and selecting custom fonts has always been a challenge. But here it’s as simple as changing your text editor font in a GNOME application. In fact everything about this application was designed to work well in GNOME.
White background and black text hard on your eyes after hours of reading. Changing between defaults is a few toggles, radio buttons, and sliders away. No need to learn using cascading style sheets.
Almost forgot, you can look up definitions and Wikipedia references.