The monks and scholars at these monasteries used a new writing system called Carolingian Miniscule that, unlike earlier script, began using lower-case letters, spaces between words, and punctuation. This allowed them to transcribe three or four pages in a day, rather than just one. As a result, over a thousand volumes survive using the new technique, versus just fifty from the previous Merovingian system.
This is also very interesting. I cannot believe that over a thousand volumes survive.