Dystopian novels tend to be grim, and Fahrenheit 451 is no exception. It has a pessimistic tone about America's future, the impact of mass media, and most people's will to go against the status quo. Innocent people are arrested and killed, family ties are weak, and most people have little education and no sympathy for those different from themselves. The recognizable science fiction technologies, such as the television walls, earbud "Seashells," and omnipresent surveillance of the Mechanical Hound, all suggest that this sort of future is not that far away from us.
Note, however, that the novel is not without optimism. There are at least two major points of hope. Firstly, Guy's character development is enormous: he goes from being one of the enforcers of censorship to an outlaw who helps keep books alive. If he can open his eyes to the injustices of his society and work against them, it seems that anyone can. Along the way, he meets dissidents and outsiders of many different types, which suggests that no matter what happens, some humans will resist tyranny and try to keep knowledge alive.
Secondly, the violence of the novel, and especially the ending, is posited as a potential opportunity for society's change and improvement. Granger references the myth of the Phoenix, in which a bird repeatedly bursts into flames and then is reborn, to argue that humanity undergoes cycles, in which dystopia is a natural but never a permanent part. This allusion reframes the war, book burning, and militarized censorship as the moment of "burning" in which the old ways will be destroyed and a new society can form. In this formulation, all the pain and suffering of the novel will clear the way for something better.