Hard sci-fi novels without an engaging plot are really hard to swallow; you can take a few pages of fully convincing explanations of how to create an artificial universe, but if what happens afterwards is not so interesting, you feel you're wasting your time. This novel is a patchwork of several stories happening to Copies, or software backups of personalities, inhabiting in different universes. Their interaction is quite ad hoc, leaving it with approximately 3-4 novellas which could have stood their own weight, but get lost by permuting it into Permutation City.