Hello,

I recently discovered this package, and thought it would be nice if
'modus-themes' supported it.

Repository link: https://github.com/chenyanming/calibredb.el

It is available in MELPA and you can install it using 'package-install'.
You also need two external packages: 'calibre' and 'sqlite3', they
should both be available in Arch Linux and Debian package repositories.

You will need to initialize calibredb database from command line by
running

calibredb --library-path /path/to/library add /path/to/book.pdf

This will create metadata.db file that can be used by calibredb.
Then in Emacs evaluate

(setq calibredb-root-dir "/path/to/library")
(setq calibredb-db-dir (expand-file-name "metadata.db" calibredb-root-dir))

and run M-x calibredb and this should start calibredb. You can then add
additional books if you need by pressing "a" in calibredb buffer.