King Arthur has issued a challenge. The first knight to find the sword Edgecalibur will be the next king. Join Sir Cumference, Lady Di of Ameter, and their son, Radius, as they race to help their friend Vertex discover the secrets of cubes, pyramids, cylinders, and cones---and find the sword! Grades 2 to 4. 32 pages, softcover from Charlesbridge.