Bradbury himself says it is all about TV making people stupid, as opposed to being about censorship by the government as all the English teachers try to tell you.
This article contains a video interview with Mr. Bradbury and quotes from it.
From the article:
“Fahrenheit 451 is not, he says firmly, a story about government censorship,” wrote the Los Angeles Weekly‘s Amy E. Boyle Johnson in 2007. “Nor was it a response to Senator Joseph McCarthy, whose investigations had already instilled fear and stifled the creativity of thousands.” Rather, he meant his 1953 novel as “a story about how television destroys interest in reading literature.” It’s about, as he puts it above, people “being turned into morons by TV.” Johnson quotes Bradbury describing television as a medium that “gives you the dates of Napoleon, but not who he was,” spreading “factoids” instead of knowledge. “They stuff you with so much useless information, you feel full.”