The besetting sin of most SF is its humourlessness; there is precious little gaiety in space. Robert Heinlein is the exception. He is so completely the master of his medium that he can afford to make fun of it. Space Family Stone [published in the United States as The Rolling Stones] is, for the most part, an agreeable send-up of the spaceways. The Stones wisecrack their way from planet to planet, doing a little trade here and there, tending the sick (Mrs. Stone is a doctor) but mainly enjoying themselves. Grandmother Hazel, who is "the only juvenile delinquent old enough for a geriatrics clinic", justifies her decision to go on to Titan: "The dull ones stay home—and the bright ones stir around and see what trouble they can dig up. It's the human pattern." Grandmother is beyond question one of the bright ones, and so is the...