Answer: They became a luxury product that was highly valued
Explanation: In the middle ages books where hand printed by someone called a scribe. These people would take a works like the bible and hand copy them. This prosses could take up to weeks some times mouths to Finnish. Then you have the another person bound the book, being a delicate prosses. So at the end of the prosses one book would be hundreds of dollars' sometime thousands. This meant the only people that could get a hold of a book, was the rich, that could read. Even when the printing press was invented. Book could still be a tad bit expansive because you still need someone to bound the books.