PC best reader Calibre usage pitfalls

Some PDFs cannot be set to dark mode, but if you use the EPUB format with the calibre e-book viewer, you can.

Right-click -> Open with -> calibre e-book viewer

After opening it, right-click -> Preferences -> Colors -> choose Dark, then check "Override colors of the entire book" to Always

Double-click a word inside, and the dictionary panel will pop up automatically. At the bottom of the dictionary panel there is a green plus "Add source". The built-in ones aren't very good; I recommend adding this dictionary:https://dictionary.cambridge.org/dictionary/english-chinese-simplified/{word}