The book Ubik, for instance, has its main character, Joe Chip, dealing with an evil entity that seems to be permeating the reality of Joe and his team of precogs.  The world surrounding Joe’s team starts moving back in time, populating the world with cars from the 1950s that gradually regress to become Model-Ts, TVs become radios, and so on. The only thing that can save Joe is a mysterious product called Ubik, which Joe can apply to himself or his surroundings to prevent this reverse entropy.  Eventually we find that the world is actually someone else’s, the imagination of a deranged and dying sociopath.  The great thing about science fiction is that it’s always an allegory for the society in which the writer and reader live.  In the case of Ubik, the reader might wonder if his/her/zhir own reality was fabricated by a deranged force.

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