An amusing time-travel novel, based on the "many-worlds" interpretation of quantum mechanics (an interpretation for which there is no evidence or requirement). Asher has the wit to steal Heinlein's answer to the question, "How come I end up in the same place on Earth when I time-travel, despite the Earth's orbit, rotation etc?" and modify it only slightly. It is also fun to get away from Asher's "Polity" setting in this novel: may his publishers allow him to do so more often!