When this book came out, my uncle gave me a copy. He is a professor of Sociology and an avid reader. He said, "This is stuff you need to think about".
It changed the way I saw the world. I grew up with a very materialistic mom who would buy anything as long as it was on sale. This book gave me a inkling into the way such a behaviour came to exist. It also validated the idea I had that just buying stuff was dumb. I was 20 and didn't really know how to phrase my intuitive feelings and Ritzer's book gave me context.
Nearly 20 years later, many people have built on the foundation of this slim volume. There are definitely books that are more detailed, complex and also very well written. I can liken it to Silent Spring: there are definitely better books on the environmental challenges we face, but as a book that concisely put together ideas in a way that non-academics can digest and incorporate in their lives, the book changed the world.
This little, simple book can pack a serious punch to a young person without looking like another textbook to read. It's a classic for those who are interested in the mechanics of our insane consumer-culture.