Gutenberg did something fundamentally important: He invented the printing press which was to cause a major explosion of literacy throughout Europe in 1500.
Prior to that point, all "books" (mainly bibles) were hand printed by monks laboriously and painstakingly copying page after page from previously written pages (and hopefully, not taking "artistic liberty" by making changes). Only the quite wealthy (and powerful archbishops) could afford bibles.
With the invention of movable type and printing presses, one could "mass produce" written works. Within a couple of decades, most people found themselves either able to afford a book or knew someone who owned one. Announcements and documents were distributed. Soon it became necessary to be literate and literacy education was "needed" by the masses.
Some early Roman (about 30 B.C.) stone writings
discovered in Mainz. This was in an area devoted to
the history of the "printed" word in the museum.
Me with Johannes Gutenberg (I'm on the right)
He's actually dead now and this is a statue.
Some early (1400 A.D.) hand printed bibles. I got
yelled at for taking flash photographs. Of course, the guy
yelled at me in German so I couldn't really understand him!
A recreation of Gutenberg's first printing plant. He even
melted the lead to make the type.
Another highlight of the trip was a stop at a medieval castle.