In many ways, twentieth-century America was the land of superheroes and science fiction. From Superman and Batman to the Fantastic Four and the X-Men, these pop-culture juggernauts, with their "powers and abilities far beyond those of mortal men," thrilled readers and audiences--and simultaneously embodied a host of our dreams and fears about modern life and the onrushing future. But that's just scratching the surface, says Jeffrey Kripal. In Mutants...