Remixed from these designs: https://www.printables.com/model/608217-book-keychain. I can't formally tag it as a remix because it was posted on a different site. The creator is https://www.thingiverse.com/snaal, go check out their stuff on Printables!

Print in place on smaller scales, may require supports for book cover the bigger you go. I uploaded a plain book file, it is easy to import into a program like Tinkercad to personalize the book covers.