Long before interplanetary exploration and a certain rock group, Robert A. Heinlein wrote this science fiction classic (Random, 1977). Mischievous teen twins Castor and Pollux Stone set the story in motion with a plan to make their fortune as space traders. Soon they are waving goodbye to their home on the Earth's moon and they're headed for Mars with their parents, sister, younger brother, and grandmother. The Stones are an intelligent, strong-willed clan, so there are squabbles during their months of weightless flight. Everyone pulls together when mother Edith's doctoring skills are needed for a nearby ship's epidemic and when grandmother and little brother are lost in the asteroid belt. In between emergencies, the twins' entrepreneurial skill help them sell the bikes they reconditioned while floating outside their spaceship and unload a horde of fertile felines called flat cats. The Stones end up headed for new destinations in the universe with renewed love and respect for each other. A well-chosen cast of 21 actors turns this half-century-old novel into a lively romp. Standouts in this pleasant company are Bill Molesky as the blustery dad and Caroline Fitzgerald as the feisty, but caring grandmother. Original music adds to the fine sound quality. Twenty-first century listeners can compare current information with Heinlein's speculation, or just enjoy this humorous family adventure. An additional purchase, but one that will be most welcome by science fiction fans in elementary, middle school, and public libraries.