Tuesdays at the Castle by Jessica Day George

syndetics-lcA castle is almost always part of a fantasy story.  But in the book Tuesdays at the Castle, this castle has a mind of its own!  It can add new rooms, an entire wing, doors, archways, a secret passageway—whatever it thinks is best.  But most importantly, it protects the royal family and people who are loyal, especially Princess Celia.  People at the castle that bring harm to the family receive small, dingy rooms and can also be shut out of other rooms by the doors disappearing.  When the king, queen, and prince are attacked outside the castle and presumed dead, the remaining prince and two princesses, and the castle, discover who the evil people are and work hard to cleverly save the kingdom.