It's a comic book without the pictures! In the world of this book, superheroes and ubervillians exist and each town has its own super-population. It's a cute idea and Estep handles it well with that slightly over-the-top feeling most comics have (at least the ones from my childhood).
Carmen catches her boyfriend, who (surprise!!) is a superhero, having sex with her best friend, who (surprise again!!) is an ubervillian - on her wedding day. Carmen vows that no one will ever be hurt like that again and makes it her life's work to unmask superheroes and ubervillians. The book deals with the (somewhat inevitable) results of her quest.
It's a rather light and fluffy read, but great fun.