One fact about the Middle Ages that only surprised people is that the great majority of books written in the medieval period were left unbound. In a technical sense they were unaccomplished codices, leaves and pages piled together but not sewn, glued or fastened in any way. Flyers in the deep sense of the word.
The medieval book was truly free. Free to scatter itself to the winds. Free to end up on a shelf and nowhere else. Free to be forgotten.
With few exceptions, all of the books we have from the medieval period are bound, spine, covers, warts and all. And that is a minority of the books written during that period. But one thing was to fill parchment with inked words, quite another to turn those parchment leaves into a codex, a bound book. The scribe and the book binder may not always be the same person, and the latter was not always available, and the resources required not readily at hand.
The relative loss of ancient and medieval manuscripts is due to many factors, like destruction and neglect. But it is also because some books never acquired a spine and were endowed with hard covers that we will never know them.
Written by hand, they were undid by time. And their words flew into tue night, unwitnessed but free.