A book by Robert Heinlein. A lighthearted zoom around the solar-system with the endearing Stone family: Castor and Pollux, 15 year old twin red-headed geniuses; Meade, their older sister; Roger Stone, their long-suffering father; Dr. Edith Stone, their mother; Lowell "Buster" Stone, their (telepathic?) little brother; and Hazel Meade Stone, the orneriest founder of Luna Free State ever to cock a pistol in zero-G (this is the same Hazel from The Moon is a Harsh Mistress, their grandmother). Sick of the routine on the moon, the Stones take off in their ship, the Rolling Stone, to Mars, the Asteroid Belt, and beyond. Fun.