This is a beautiful edition. And the critical commentary by Terrence Gordon provides a helpful structure for getting your mind around McLuhan's ideas.
Although this may be McLuhan's great work, it is not best place to start. It is long and often incoherent. On page 39, McLuhan introduces a notoriously difficult metaphor that he uses through the book. It concerns hot and cool media. "Hot media are ... low in participation, and cool media are high in participation or completion by the audience." So, he explains, hieroglyphics and photographs are hot, but the phonetic alphabet and cartoons are cool. Radio and movies are hot, but the TV and the telephone are cool.
Does that make any sense? If not, the better place to start is his earlier work, The Gutenberg Galaxy. It is shorter, and the logic is much easier to follow. It lays out the basis of McLuhan's thinking about how changes in media reshape culture. If you are a systematic thinker like me, it is a far better book to get the basics of McLuhan's analytical method and ideas.
Even if you have the basics, UM is a dense, inspiring, and unsettling work. In each of the 33 chapters, McLuhan makes connections that change the way I think about culture. But just as often, he makes some nonsensical analogy or leap of logic and then fails to explain it.
In the end, it helps to stop trying to understand UM and let it inspire you to think.
In other words, it is very cool.