An addition to Asimov's series of robot-detective novels, and a more convincing effort than The Robot of Dawn (1983). Nearly two centuries after the death of Earth detective Elijah Baley, Settlers--short-lived, disease-ridden, dynamic pioneers from Earth--have begun to colonize the galaxy. By contrast, the long-established, long-lived, aristocratic, robot-dependant Spacers have started to decline. So, Spacer planet Aurora's head-cheese Kelden Amadiro, still smarting from his long-ago defeat by Baley, teams up with unpleasant, ambitious robotics whiz Levular Mandamus to plot Earth's destruction and thus halt Settler expansion. Meanwhile, Baley's old flame Gladia joins D.G., a Baley descendant from the Settler planet Baleyworld, to investigate some lethal goings-on on the recently-abandoned Spacer world, Solaria. Also, ostensibly accompanying Gladia but actually running the show, are robots Giskard (he secretly has the power to read and adjust emotions) and Daneel, the humaniform detective and Baley's former partner. As the plot lines intertwine, the human drama that ensues is decidedly tame and talky, from standard fulminating villains to tepid romancing. However, the real heroes here are Giskard and Daneel, as they grapple with the case and with the restrictions imposed on them by the built-in Three Laws of Robotics--and grope towards a solution that transcends everything. A satisfying plot, then, marred by perfunctory backdrops and fairly mundane human doings--but scintillating and stimulating whenever the robots occupy center stage.