[moggie]

You also need to delete the file metadata.db

Originally Posted by kovidgoyal

Wow how did you manage that?

I takes real ability

Originally Posted by kovidgoyal

Delete/rename the database file, it will be recreated, though you will lose any metadata stored in the database.

I cleaned everything out by

cd Library/Preferences
rm -rf calibre net.kovidgoyal.calibre.plist