[SlickRCBD]

I was trying to resync the calibre library manually on two computers when I accidentally copied the entire contents of one computer's library into the other's.
While originally they were one and the same, there were many new "books" downloaded with fanficfare in the main computer and two new "books" downloaded with fanficfare on the other.
Is there any way to get calibre on the main computer to scan the library folder and re-add any books not already in the library in such a way that I can still use FanficFare to update the stories that might have been updated?

I'm not sure if just trying to drag and drop the folder and skip any duplicates would set up fanficfare to know where to check for updates or not, so I'm asking the best way to fix this situation.