Tuesdays at the Castle by Jessica Day George

On Tuesdays, the Glower Castle switches it up - a new room appears or halls are rearranged. Princess Celie, one of the royal children, tries to map out the castle and keep up with all of the changes.

When King and Queen Glower mysteriously disappear, the Castle knows that something is wrong. Officials from neighboring countries are convinced that the king and queen are dead and they come in to attempt to take over, but the Castle isn't going to let that happen.

Overall, this was a whimsical book to read. The first half moved a lot faster for me than the second half though.

Thanks to Grace for the recommendation!