The Golden Rectangle (Paperback, Reprint)

Two girls with very different superpowers join together to save the world from a tiny tyrant in this sequel to "The Secret Spiral."
Flor Bernoulli, a fashion maven from Brooklyn, New York, and Lucy Moon, a horse-rustling farm girl from Georgia, are both in possession of magic keys that give them special powers. And they're going need those powers if they have any hope of saving the universe.
Only four inches tall and made of nothing but squares and rectangles, Square Man is on a mission throughout the universe to destroy anything round or curved. And it's up to Flor and Lucy to stop him. Helped by Dr. Pi, a pie-baking wizard thousands of years old, and Buddy Moon, Lucy's father and owner of an ice plant, this fantasy adventure takes the girls on a romp through time and space...and introduces a bit of magical math at the same time.