I also find it interesting that our characters don't read much. Catherine reads anything she can get her hands on. Of course, in the twelfth century, this wasn't much but she would have read the entire works of Peter Abelard, since the convent where she studied was run by his wife. She also would have read bits of saints Augustine and Jerome and may have snuck in some Virgil and Ovid. Even after she left the convent, she may well have had a psalter, a book of psalms, to read.
Actually, the amount of graffiti on medieval walls indicates that many people were able to write in their own language, at least the more scurrilous words. Even if he hadn't been marked for a career in the Church, Edgar would have learned to read. This is good because merchants and craftspeople were already keeping books of what had sold, when, to whom and for how much.
Solomon probably read as much as was necessary but not in Hebrew. The great eleventh scholar, RASHI, had to gloss Hebrew with Old French because many of his students didn't understand it that well and used the translation above the text.
But the sort of literature we write; romance, adventure and mystery, was, as Priscilla said, oral. Plenty of people could recite long passages of The Pilgrimage of Charlemagne or the Jeu d'Adam. The first of the Crusade cycles were being recited and sung in courts and taverns, along with sometimes, ok often, obscene parodies of solemn religious songs.
The effigy of Eleanor of Aquitaine on her tomb shows her reading. Maybe it was a book of pslams but it might also have been some racy poetry by one of her friends.