Currently I’m using booky mcbookface but the app is really lacking and the scrolling is not smooth.
Edit: I came across Lithium and Readera which both don’t seem to collect much information compared to other apps. Not sure if they’re open source though.
I dunno about favorite but I use Calibre when I want to read an epub directly on my laptop or some f-droid app (name forgotten) on my phone. Really though I prefer plain luddite text files. I convert epub to text with pandoc, then use either “less -r” or emacs view-mode to read the text file.