The title is quite clever, because at 451 degrees Fahrenheit, paper combusts.
The son-of-a-bitch Michael Moore used the title's theme in his movie "Fahrenheit 9/11", to Ray Bradbury's disapproval.
Guy Montag works as a fireman, which burn books instead of put fires out because houses are fireproof in the future. On one alarm they find a old women on a pile of books in her house, in rebellion against society she lights her books and herself on fire. Before she does that Montag steals a book. He wonders if something in the book will fix his life and make it happy.
He stores it with other books he stole. Beattey knows he stole a book and warns him to burn it. One day they get a alarm and arrive at his house. Beattey gives him a flamethrower and he burns his house down. Beatty taunts him and assaults him and Montag burns him alive. He makes it out of the city to a group of outsiders who read books. They start going away from the city and a nuclear bomb is dropped on it. They decided to head back to the cities ruins and teach surviver's etc. about how life use to be.