Hey,
would be great to have also a possibility to read DJVU files in the browser, maybe based on this viewer: https://github.com/mateusz-matela/djvu-html5
I decided to focus on the more "modern" and common book formats: epub, cbx (for comics) and not implementing every different book format.
So I'm not going to implement it.
I have implemented this in PR #1713 by integration of proposed djvu-html5 viewer which is however quite memory hungry (for thick scanned books) with modest UI, but for start it is good enough IMO.
As next step I would consider replacing it with djvu.js which is much faster and does not eat up RAM. However it's UI is currently not suitable for reading books (mainly on mobile).