This novel is about individuality, the scare tactics employed by the "mob" (masses), and how one can bring an end to the other.
The fact that Bradbury chooses reading and books as the example of free thinking is part of his own romantic relationship with books and reading. Free thinking and individuality could have been expressed with similar power if he were to choose any form of art, or even sport.
However, this is where his novel connects to the world today and where it connected to the world when the novel was written - television and image-oriented media seem to be taking the place of books as the principal vehicles for the exercise of imagination.
One problem the novel highlights is the problem of a possible loss of interest in the printed word and in reading -- problems that do exist today to some degree, although not for the reasons Bradbury imagined.
Ideas by their very nature are dangerous. Concepts embodied in books can cause people to realize someone else's ideas, think about them, question them, and act upon them, something that a totalitarian society will never accept.
The totalitarian society will tell you how you will conduct the business of living your life, because it benefits those who control the totalitarian society. Removing ideas removes the ability of challenging the society.
The book is a dystopia, or a supposedly perfect world gone wrong. All dystopias are warnings. Bradbury has often written about threats to our humanity, such as television and not reading. His stories are haunting, but meaningful because we can see aspects of them in our daily lives.
I'd say his purpose was to warn about the dumbing down of our culture. He was saying that we don't care about intellectual stuff or thinking or anything like that. All we want to do is watch TV and be entertained. He might think that this is even more true today than when he wrote given that we know have the internet and video games and other such things that give us even more kinds of mindless entertainment.