What I do in this situation is a little better, as it allows storage of any files, but still uses calibre as the Dbase.
Make an empty book as normal, and edit the metadata as you see fit.
Then make a folder in your Documents, or where ever you want to store all your related files. create a shortcut to this file, and drag it on to calibre so it makes an entry. Then just merg the two entries, keeping the lnk and metadata.
You could make the folder first and just drag it in, then change metadata to suit.
This means Calibre only has the .lnk in the database, and all your files are in your own folder structure, easy to copy move backup and add to as you need. This is great for files that calibre does not support.