I'm wondering this too. I also thought about setting up calibre as I own a ton of drm free books and while the calibre reader itself is nice (the viewer is all I mainly use), sometimes I do find myself wanting to read on my phone while at a dr appointment or whatever

I tried both Grimmory (current booklore) and Calibre Web Automated, and I prefer the latter. You can also add Shelfmark to CWA to download books.