It used to be fairly respectable to believe that John F. Kennedy was killed as the result of a conspiracy. Both the polymathic genius Bertrand Russell and the philosopher Richard Popkin, who wrote a history of skepticism, thought the Warren Commission was wrong when they concluded that Lee Harvey Oswald acted alone, as did, eventually, several members of the commission itself. A special congressional investigation into the matter concluded that Kennedy “was probably assassinated” — yes — “as a result of a conspiracy.” But over the years, something changed. A taboo descended on the discussion, such that Christopher Lasch, the author of The Culture of Narcissism, would write that “the most remarkable feature of the assassination is not the abundance of conspiracy theories, but the rejection of a conspiracy theory by the ‘best and brightest.’” I am neither the best nor the brightest, but I too concluded long ago that there was nothing all that complicated about the JFK assassination, for the simple reason that a plot so huge could never stay hidden. But then I read this masterful examination by Scott Sayare of what we know, and what we still don’t, about that day in Dallas 60 years ago.