Sir Cumference and his wife, Lady Di, are back in another math adventure. As the hosts of a surprise birthday party for King Arthur, the couple needs to organize a growing number of guests for events to run smoothly. After several fumbling attempts to count the crowd, Sir Cumference realizes that the simplest way to figure out the total is to group the guests into tens, hundreds, and ultimately thousands. This system allows the royal celebration to take place without a hitch, resulting in a happy ending for all. Children will enjoy the lesson built into this tale and identify with the birthday-party theme. While the story can be enjoyed independently, most youngsters would benefit from sharing the book with an adult to fully understand the place value system. The math concept is explained in more detail in an author’s note. The painterly acrylic illustrations convey the action with humorous exaggeration and amusing details (the depiction of a farmer and his wife is reminiscent of Grand Wood’s “American Gothic”).