EF is exceptional in handling many file types well. Even formats it does not “know” about can still be manipulated, but they show up in the Record Viewer as icons.
Meanwhile I’m finding it painful to manage my eBooks, especially the ones I use for research. Calibre does some management, but it’s not nearly as flexible or good for searching as EF.
Could you include some book formats in EF? I don’t know which are the key ones, but ePub seems to be the main open source format, plus whatever Kindle uses. Thanks!