Good question.
Personally, what I do is to convert the epub to htmlz format by using Calibre. Then unzip the htmlz file (it's just a zip file really), and load the html file into the web browser, and then I can use the Migaku Browser extension (or Yomichan).
It's a Kanji learning resource:
It teaches radicals, meanings and readings of kanji, and then vocab using those kanji to reinforce them. Every item is separated into 2 cards for meaning and reading.
It takes things more slowly but by about level 15 you'll have all the N5/N4 kanji as well as about 50% of the N3.
It is VERY thorough. Some people say it is more thorough than necessary, and that is a valid criticism. It beats kanji to death. But the upside is that you really know your kanji and are familiar with multiple readings and vocab for each.
There's a phone app companion called Flaming Durtles.