Worlds of the Imperium is a science fiction novel by American writer Keith Laumer. It originally appeared in Fantastic Stories of the Imagination between February and April 1961. The following year it was published by Ace Books as an Ace Double with Seven from the Stars by Marion Zimmer Bradley. It is an example of an alternate history novel in which a man from our reality becomes involved with another parallel world in which the American Revolution never happened and the secret of inter-world travel came under the control of the British Empire, which forged a unified Imperial world-state known as the Imperium. Source: Wikipedia (en)