I have a custom column of type=text, called "#origfile", which I use to store the official Amazon filename of my books. (This allows me to download the book with the Amazon book metadata -- pagenumbers and annotations -- then overwrite the book with my calibre copy that has fixed title/authors.)
The only real trick is making sure to always copy over that info (NOT the file extension, though
) whenever you add a new book -- and, the first time, adding in the data for all your current books
!