In my hobbyist understanding of history, I get the impression that literacy following the Roman Empire was much lower than during the Empire. The idea of monks painstakingly copying text in monasteries explains why literacy and written sources in general would be hard to come by before the printing press.

So how did the Romans do it? I imagine literacy was still low compared to modern times but how did texts like Caesar’s conquest of Gaul, various military manuals, the numerous Roman historians, etc. reach our era without wide spread distribution? Especially since it’s presumed that loads of written material has been lost over the centuries, it appears the Roman publishing industry must have been pretty sophisticated. How did the Romans copy and distribute these well known texts?