I have a few suggestions to improve the UX and make this already nice project more friendly (ordered by importance in my opinion ):
Fullscreen button
Dark/Light mode toggle
Blue light filter option
Web search for selected word/sentence
Loading and showing the current page first then load the rest in order, instead of loading the whole book at once in the beginning as I encountered a long loading time when I tried big epubs.
I have a few suggestions to improve the UX and make this already nice project more friendly (ordered by importance in my opinion ):