POW! (How far should I go to protect my rights?) BAM! (What's my position on gay marriage?) ZING! (Look out for that embedded reporter!) In today's comic books, superheroes aren't just thinking about how to defeat the usual kryptonite-wielding villains. They're also tackling topics such as terrorism, war, and civil liberties as a heavy dose of 21st-century reality seeps into their alternate universe. In Civil War, a sprawling new Marvel series, superheroes like Spider-Man and Captain America must choose sides over whether the government should be allowed to register them. In a comic book called Ex Machina, a 9/11 hero-turned-mayor...