From every imaginable point of view, the story of the Cuban revolution is a tragedy. How to make sense of that story is quite another matter. Like all tragedies, Cuba’s is haunted by unanswered questions, fatal mistakes and sliding-doors alternative possibilities. As is customary in the genre, what we think of its protagonists is a subjective question, determined by perspective more than anything else. Every viewer of Shakespeare’s “Julius Caesar” must draw their own conclusions about Brutus and Marc Antony; so too with Fidel Castro and Che Guevara. During the decades when “actually existing socialism” (as its defenders called it) held sway over something like a third of the world’s population, Cuba looked, at least sometimes, like an exceptional case. Unlike the forbidding pseudo-socialist regimes of Eastern Europe and the Soviet Union, the Cuban revolution was not imposed by military force or an ingenious coup engineered by a “vanguard party.” It was a cinematic and charismatic adventure, beginning with a daring band of guerrillas in the Sierra Maestra mountains who swept through the country until …