Written by hand, medieval manuscripts are very different from printed books, which started to appear after Gutenberg’s mid-fifteenth-century invention of moving type. One difference in particular is important for our understanding of manuscripts. While printed books were produced in batches of a thousand or more, handwritten copies were made one at the time. In fact, medieval books, especially those made commercially, came to be after a detailed conversation between scribe and reader, a talk that covered all aspects of the manuscript’s production. This is the only way the scribe could ensure the expensive product he was about to make was in sync with what the reader wanted. Consequently, while printed books were shaped generically and according to the printer’s perception of what the (anonymous) “market” preferred, the medieval scribe designed a book according to the explicit instructions  of its user.

This principle of one-on-one (of scribe-reader and reader-manuscript) explains why we come across some very strange…