Actually, the title was a mistake. When the book came back from the typesetter’s, it had on the cover “Massage” as it still does. The title was supposed to have read “The Medium is the Message” but the typesetter had made an error. When Marshall saw the typo he exclaimed, “Leave it alone! It’s great, and right on target!”
Now there are four possible readings for the last word of the title, all of them accurate: “Message” and “Mess Age,” “Massage” and “Mass Age.”
Each medium, independent of the content it mediates, has its own intrinsic effects which are its unique message.
The message of any medium or technology is the change of scale or pace or pattern that it introduces into human affairs. The railway did not introduce movement or transportation or wheel or road into human society, but it accelerated and enlarged the scale of previous human functions, creating totally new kinds of cities and new kinds of work and leisure. This happened whether the railway functioned in a tropical or northern environment, and is quite independent of the freight or content of the railway medium. (Understanding Media, NY, 1964, p. 8)
He also wrote the following in Understanding the Media, decades before the World Wide Web became a popular, well, medium:
“By putting our physical bodies inside our extended nervous systems, by means of electric media, we set up a dynamic by which all previous technologies that are mere extensions of hands and feet and teeth, will be translated into information systems. Electromagnetic technology requires utter human docility and quiescence of meditation such as befits an organism that now wears its brain outside its skull and its nerves outside its hide. We must serve our electric technology with the same servo-mechanistic fidelity with which we once served our coracle, our canoe, our typography, and all other extensions of our physical organs. But, there is a difference here. Those previous technologies were partial and fragmentary. The electric is total and inclusive. An external consensus or conscience is now as necessary as private consciousness. With the new media, however, it is now possible to store and to translate everything; and as for speed, that is no problem. No further acceleration is possible this side of the light barrier.”
The website run by his estate is here.
Full disclosure: He is Canadian.