One of the most obvious themes in the novel is how important it is for individuals to refrain from rushing through life. In essence, Bradbury makes the point that “you should stop to smell the roses” but more eloquently and meaningfully than this trite platitude is able to do. Bradbury’s futuristic society consists of many individuals who drive their cars (called beetles) at extremely high velocities, watch interactive TV at extremely high volumes, listen to in-ear radio devices much like an iPod, and rarely pay attention to the small things in life. Clarisse is an exception to this rule, but since she is killed by a car that was speeding down the road, she is nonetheless greatly impacted by this lifestyle.
Another prevalent motif is Bradbury’s opinion that abridged versions or summaries of books lead to the type of society that exists in his novel. In one of Beatty’s stories about how the world came to be the way it is, he says that great pieces of literature gradually became more condensed until they ceased to be substantial. This is similar to the previously discussed theme. Ironically, study-guides, like the one you're reading, may be an example of the same tendency.
The theme concerning mankind’s failure to learn from its past is more prevalent near the end of the novel. When the war starts, Granger compares this failure to the endless cycle that a phoenix goes through burning itself and rising from the ashes, but notes that humans, unlike the phoenix, are able to remember the stupid things that they did.