spies to others on Earth, and sets out to prevent them. Reception Galaxy's Floyd C. Gale reviewed the novel favorably, calling it the best of the Lucky Starr series and saying that Asimov "milks the situation for all its thrills, while painlessly imparting scientific lore and a code of ethics." Villiers Gerson, writing in The New York Times, declared it to be "well-written adventure". Themes The introduction of the Sirians in Lucky Starr and the Pirates of the Asteroids marked the beginning of Asimov's transformation of the Lucky Starr series from the 'masked crimefighter' subgenre to the espionage subgenre. For the next two novels in the series, the Sirians served as a distraction from the real solution to the mystery; but in Rings of Saturn the Sirians are villains in fact. As with Lucky Starr and the Big Sun of Mercury, the Three Laws of Robotics plays a part in the novel, revealing Asimov as the true author, though for the sake of continuity the novel was published under the pseudonym 'Paul French'. The Lucky Starr series was written over a period of six years, during which Asimov also wrote his first two robot novels and The End of Eternity. Consequently, there are small inconsistencies between the various novels. In the first, Ganymede is mentioned as a settled world of the Solar System, although in later novels Ganymede has no permanent settlement, and has even served as the location of a secret Sirian base. The first man on Mars is named Wingrad in David Starr, Space Ranger, but is named Ching in Moons of Jupiter. The name of the state that rules the Solar System also changes from novel to novel. In Pirates of the Asteroids, it is the Terrestrial Empire; in Oceans of Venus, it is the Solar Confederation; in Big Sun of Mercury, it is the Terran Federation; and in Moons of Jupiter it is the Solar Federation of Worlds. The book has a number of plot points in common with Asimov's later novel Robots of Dawn. In both novels, the investigator manages to come up with the solution when half asleep, but forgets it when awake, and considers a psychic probe as a possible way of digging it out. In both cases, the robot responsible for the deed gives itself away by finding an unconscious person despite the odds; Mutt, by infrared vision despite the impossibility of