Which epubs on disk have been returned?

I use ADE to get books from my local library.  After I've read them they expire or I return them.  However, ADE leaves the epub file on my hard drive.  Is there an easy way to remove these expired/returned epubs from my hard drive?  So far, the only way I've found to do this is to try to open a file, and if it can't be opened then I know it's one that should be deleted.  But that gets really tedious.  Is there a better way?