Hub Cap Digest is a book that is owned by The Kanker Sisters. It was only seen in the second episode, "Nagged to Ed," when Edd was seen searching through their bookshelf. Edd thought it would be an interesting book; it could be possible that Edd likes hubcaps, or that to him this was the most interesting book on the Kankers' bookshelves. However, when he opened it, he realized that all of the pages inside were blank. The name suggests that the book is, or was intended to be, about hubcaps, even though all the pages are blank.
- The fact about the pages of the book being blank is probably a tongue-in-cheek reference to the fact that books in animated cartoons are usually full of unreadable text (specifically, scribbly lines) or are just plain blank, yet the characters reading them seem to understand the content of the books. The unreadable text (or, in this case, blank pages) is designed to save the animators time so they won't have to draw the same tiny message repeatedly.