http://isbndb.com/book/game_of_thrones_4_copy_boxed_set for example contains the first 4 books of the Song of Ice and Fire and has a barcode/isbn that's different from the books included in it. How is this information supposed to be stored - multiple barcodes on one edition, multiple editions linked to one box set edition, something else entirely? What if the books in a box set are available separately as well?