A busy triangle gets tired of holding up roofs, being slices of pie and halves of sandwiches, and even of doing its favorite activity — slipping into place when people put their hands on their hips. It thinks life would be more interesting if the local shapeshifter gave it one more side and one more angle. And so the triangle is transformed into a quadrilateral. Although as a quadrilateral it is a television screen, a window frame, and more, it soon grows tired of that shape, too. Each time it tires of its shape, it asks the shapeshifter to add another side and angle. The triangle successively becomes a pentagon, hexagon, and heptagon . . . until it has so many sides it doesn’t know which side is up! Not surprisingly, it asks the shape-shifter for its old shape back and then is content to be a triangle again. The colorful illustrations and engaging text make a great introduction to shapes and geometry. A guide at the end includes background information and suggestions for extending children’s learning.