For us, a book is, without much thought, a Κώδικας (codex), i. e. an object to leaf through. But there is much more in libraries than such books. This paper focusses on single leaves, not fragments left over from what used to be whole books, but those that were created as single sheets. Admittedly, almost all of them have only survived because they have found protection under book covers, either temporarily or until today.

Despite all the losses, more material has survived than many people realize. Notwithstanding the obvious impossibility, an attempt is made to systematize them, whereby the use of single leaves is a central aspect: they are part of works of art, served as gifts, individual leaves are templates/pre-products or merely used as scrap paper, they bear inscriptions, set law as charters, single leaves were found in public space as advertising or bullying. They functioned as teaching material, in private they can be used for private devotion, as playing cards or magical amulets.