Author Cara Stevens didn't know much about the K-Pop super group BTS until she saw them perform at the Billboard Music Awards. "I was blown away by their amazing choreography and their positive energy," she told InsideEdition.com. Shortly afterward, Stevens began work on her book, "BTS: Rise of Bangtan." It's a look at the group and its incredibly enthusiastic fans, known as ARMY. "It's really a very, very deep fan base and they're a wonderful, wonderful, supportive group of people," she said.