I am currently reading Then Everything Changed: Stunning Alternate Histories of American Politics: JFK, RFK, Carter, Ford, Reagan, by Jeff Greenfield. What if JFK did not survive to his inauguration? What if RFK did? How would history have turned out differently? For more, see this New York Times review.
Of course, the reason it is featured here is the interesting flag graphic on the cover, with the stripes on the American flag veering off in unforeseen directions.