The House in the Cerulean Sea by T.J. Klune

The House in the Cerulean Sea by T.J. Klune is a heartwarming fantasy novel about Linus Baker, a quiet, by-the-book caseworker for the Department in Charge of Magical Youth (DICOMY). Linus is assigned to investigate a top-secret orphanage on Marsyas Island, home to six dangerous magical children—including the Antichrist—and their mysterious caretaker, Arthur Parnassus. Over a month, Linus falls in love with the children and Arthur, ultimately choosing to protect their "found family" and challenging his own rigid, bureaucratic life.