They didn't exist as mass market products. Printing was expensive, so they were only accessible to the rich and literate. With one exception being the clergy.
You should probably read the Cheese and the Worms, about how an average cheese seller in 1500s Germany read hundreds of books and talked about them passionately. Printing was expensive in the beginning of print but book historians have demonstrated convincingly that there was a huge circulation of books and copied media (i.s. teams of professional copyists) pre and antedating the printing press. Less than 30 years after the introduction of the press humanists talked about how the flood of books was so massive that no one could read them all in a lifetime. You are operating on an image of print that is historically wrong.
The sheer amount of work and content you are dismissing as "nothing apart from musical scores or theatre plays" is mind boggling.