No, cheap books came from the invention of cheap printing. But the quality of works was going down because printers were just printing with zero copyright protections. Copyright is what brought the wealth of works worth reading that were then printed using cheap printing. If the only money is in private works for private libraries, that is where the quality stuff is going to go.
Making the avenue of creating for the average person also the avenue for the most income was huge in creating our modern literature landscape.
> Copyright is what brought the wealth of works worth reading that were then printed using cheap printing
Evidence for this statement?
> If the only money is in private works for private libraries, that is where the quality stuff is going to go.
Evidence that this ever happened?
> Making the avenue of creating for the average person also the avenue for the most income was huge in creating our modern literature landscape.
That only leads to higher quality (as you claim) if your definition of higher quality is "what the average person buys".