Calibre is a local single user software. There are tools like calibre-web that bring a calibre backend into a multiuser web application but even then you are not supposed to host the calibre database on network storage IIRC.

Grimmory is a web application first which is what I want. Access for my friends and, more importantly to me, an always online library with progress sync across all my reading devices.

Calibre still has some good use cases though like drm stripping and has a better workflow for heavy metadata editing, but my book sources generally come drm free and have good metadata.