The magician king

In the land of Fillory, Quentin Coldwater, now a king, feels restless, but after a royal hunting excursion ends on a sinister note, Quentin and Julia, a high school friend and a Fillory queen, charter a ship and set sail for adventure--which sends them straight to Quentin's parents' house in Massachusetts, where they uncover a new threat more dangerous than anything they have faced before.