Wednesdays in the Tower by Jessica Day George (author) (US edition)

A castle that keeps rearranging itself. A royal family sworn to protect it. Can you think of a more magical idea for a book? We think not! Hogwarts-style fantasy meets a royal kingdom in this bestselling sequel to Tuesdays at the Castle. Castle Glower is always creating new rooms. Now Princess Celie’s brother, Rolf, has dared her to catch it red-handed. No problem. She knows the place better than anyone else. Celie soon finds the room. Only – there’s a giant egg hidden inside it. The castle wants Celie to care for the egg and the creature it hatches. But what is this strange pet? And what else is the castle hiding?