Imagery is one of the strongest devices available to a writer. Put simply, imagery allows the writer to string together words in a way that creates mental images, helping the reader visualize a scene or a metaphorical concept. In this quote, Bradbury uses the literary device of imagery to great effect.

The world is described as having once been "roomy," a comfortable piece of imagery that may awaken thoughts of a comfortable living area that one has all to themselves. However, the world has since become full of "eyes, elbows, and mouths." This obviously refers to human beings, but the use of these particular body parts can awaken a particular discomfort in the reader. With the imagery of the world as a "room" still in mind, one can now imagine it filled with people watching each other, bumping their elbows together uncomfortably, and hearing cacophonous noise from all of their mouths.

This quotation uses the literary device of synecdoche, a term which means that the part stands in for the whole. In this case, the words "eyes and elbows and mouths" are used to mean human beings. Obviously, humans consist of far more than these three body parts, but when we read those words, we understand that Beatty is talking about people.

He says that people moved away from reading books as the population grew larger and as other media were invented, such as photography, movies, radio, and television. Books were complex, Beatty argues, and people, who became a mass (hence his referring to them as undifferentiated eyes, elbows, and mouths) rather than individuals, started to wish for information that was much simpler than what a book might offer. Rather than deal with difficult texts, says Beatty, the masses wanted information to be simplified: "books leveled down to a sort of paste pudding norm." Following that, they didn't want books at all.