Based on what you know, it should not be a surprise that most early medieval literature was written in Latin. Latin was the language (both spoken and written) of the educated during the Early Middle Ages, and most of these educated people happened to be monks.
Texts were translated and written by hand (often in poor lighting) by monks who filled pages with words and complicated illustrations. Most, if not all, books were written by hand over long periods of time, until a man named Johannes Gutenberg invented the printing press in the early 1400s and made everything much, much easier.Books could be produced faster than before, though the letters had to be carefully arranged before being pressed to the page, and this too took quite a bit of time. But what tales and stories come from the medieval period? more