“Worlds of the Imperium,” Keith Laumer, 1961 — (excerpt) A man stands in a field as his body morphs and rides the time tide.
Comments: Excerpt read read in A Century of Science Fiction, ed. Damon Knight. First published in Fantastic, Feb. 1961. Knight notes that Laumer advanced a major new idea in time travel, the first one perhaps in 20 years. “The idea is just this: that events may be ordered, may have a logical sequence, across the sheet of parallel universes. Think of time as an endless series of film strips laid side by side, each strip almost identical to the adjoining ones. Now, if you were to taek one frame from each strip, moving at right angles across the series of strips, and then combine these frames into a new sequence…”
Wikipedia: (novel) “Worlds of the Imperium is a science-fiction novel by Keith Laumer. It was originally published in 1962. 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.”
Author: Wikipedia: “John Keith Laumer (June 9, 1925 – January 23, 1993) was an American science fiction author. Prior to becoming a full-time writer, he was an officer in the United States Air Force and a U.S. diplomat. His brother March Laumer was also a writer, known for his adult reinterpretations of the Land of Oz (also mentioned in Laumer’s The Other Side of Time).”