Sounds like The Last Book in The Universe by Rodman Philbrick. The protagonist is a teenage boy suffering from epilepsy. I had chanced upon it in high school.
It's the story of an epileptic teenager nicknamed Spaz, who begins the heroic fight to bring human intelligence back to the planet. In a world where most people are plugged into brain-drain entertainment systems, Spaz is the rare human being who can see life as it really is. When he meets an old man called Ryter, he begins to learn about Earth and its past. With Ryter as his companion, Spaz sets off an unlikely quest to save his dying sister -- and in the process, perhaps the world.
Very few people know how to read or write, and the protagonist winds up carrying the last book in his head.
He is accompanied by Ryter, an old man that he tried to steal from in the beginning of the story and one of the last few people remaining who can read and write...