It's been a decade since Carrie Underwood swept the fourth season of American Idol, kicking off a career that would quickly make her the biggest country female artist since Shania Twain. She's straddled the border between country and pop music since then, armed with a string of crossover chart-toppers ? many of them self-written ? that mix the sweep of larger-than-life power ballads with the pissed-off swagger of revenge songs. Storyteller, which hits stores this Friday, plants its flag in a similar intersection, rolling mandolins and synthesizers into the same genre-bending package.