Captain America isn't just another superhero: He embodies a national identity and geopolitical ideology. Or so says Jason Dittmer in his new book, Captain America and the Nationalist Superhero. Cap, according to Dittmer, is the prototype of the "nationalist superhero," a comic-book subgenre that uses superheroics to validate the nation-state and vice versa. His rippling muscles and equally rippling sense of morality reflect and fuel the myth of American exceptionalism and justice. Noah Berlatsky disagrees, arguing in his review that the nationalist superhero has become an object of nostalgia. Today's most popular fantasies—and nightmares—involve power without borders.