The Cracks in the Kingdom, by Jaclyn Moriarty, was published in 2014 by Arthur A. Levine. It is the sequel to A Corner of White.
Princess Ko’s been bluffing about the mysterious absence of her father, desperately trying to keep the government running on her own. But if she can’t get him back in a matter of weeks, the consequence might be a devastating war. SO under the guise of a publicity stunt, she gathers a group of teens from across the country to play to the media in a series of carefully orchestrated photo ops. In reality, each of these teens has a special ability, and together they will attempt to crack the unsolvable case of the missing royals of Cello. Chief among these is farm-boy heartthrob Elliot Baranski, more determined to find his own father than ever. And with the royal family trapped in the World with no memory of their former lives, Elliot’s value to the Alliance becomes clear: He’s the only one with a connection to the World, through his forbidden communications with Madeleine Tully. Together, sharing notes, letters, and late nights, Elliot and Madeleine must find a way to travel across worlds and bring missing loved ones home.