Genre of 11/22/63

Charles McGarth at the New York Times has posted an interesting article on Stephen King's new book. His article focuses primarily on the genre. McGarth call the book a "counterfactual" novel -- a book that imagines what would happen if historical events turned out differently.
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McGarth gives us a sampling of some popular counterfactual books out there. He writes: Mr. King is no stranger to parallel or alternate universes, but for him this is a rare foray into alternate history. In American fiction, perhaps the groundbreaking instance of this genre is Philip K. Dick’s 1962 novel “The Man in the High Castle,” which imagines that the Axis had won World War II. More recent examples are Philip’s Roth’s novel “The Plot Against America” (2004), in which Charles Lindbergh beats Franklin D. Roosevelt in the 1940 presidential election, ushering in an era of American fascism and anti-Semitism, and the just published collection of novellas “Then Everything Changed,” by Jeff Greenfield, which actually upends Mr. King’s premise. It has Kennedy being assassinated three years earlier, not in Dallas but in Palm Beach, Fla. http://artsbeat.blogs.nytimes.com/2011/03/02/what-if-in-next-novel-stephen-king-imagines-a-chance-to-alter-the-jfk-presidency/