What are the social and political impacts of the printing press in a society?

In the era before Gutenberg invented the printing press, books were copied by hand, usually by scribes from the Catholic Church, or by the few literate people in a society. This restricted the flow of information and created what philosopher Harold Innis called a "monopoly of knowledge"-- a society where a select few (often members of the dominant religion) decided what would be preserved, what would be published, and who would be allowed to read it.

Once the printing press came along, books (and later, magazines) could be mass-produced, printed in greater numbers and made available to a wide range of people. This made literacy more attainable, since now, many people could own books and learn to read them. It also meant that wider ranges of subject matter would be printed: at first, it was only religious books, but the public soon demanded fiction, poetry, adventure tales, and humor; selling books provided authors with income and readers with entertainment.

But this new access to printed materials also created problems for those who wanted to restrict the flow of information: to cite one example, in 1735, in the then-British colony of New York, newspaper publisher John Peter Zenger saw his printing press smashed by soldiers, when what he had published displeased the royal governor. That is why what we call "media" today used to be called "the press"-- having access to a printing press made it possible to publish and spread news. Some historians believe that Zenger's encounter with censorship ultimately led to the First Amendment, which guaranteed journalists and reporters the right to print the truth as they saw it-- "freedom of the press."