To save people the search, a GIS of this will suggest the results "giant fourteenth century tomes" in Prague. And indeed, while most medieval books were far smaller, the oversized codex had a distinct place in the Middle Ages, at the intersection of practicality and ostentation.

The most common use of giant codices was liturgical, that is, for church services. Typically, this would mean a lectionary or Bible for the reader to read from or to display so the closest people might also see the words (other clerics). Another common use is choir books, the large suze allowing more singers to see the same page from farther away.

But oversized manuscripts, especially in the parchment days, were UNGODLY expensive. So any large book wasn't "just" a practicality. These were lavish luxury objects, often fancifully illuminated and maybe put on display when not in use. Patronage for a giant manuscript was a marker of social status as well as a donation towards orayers for one's speedy passage through purgatory.