Permutation City explores the philosophical implications of digital consciousness in a near-future where wealthy individuals can upload their minds to computer simulations and achieve a form of immortality. Greg Egan, an Australian science fiction writer known for his rigorous engagement with physics and philosophy, follows Paul Durham as he experiments with copies of himself to understand the nature of identity and reality when consciousness can be duplicated, modified, and run at different speeds. Durham creates an entire simulated universe with its own physics, where uploaded minds can live indefinitely—but the relationship between simulation and reality proves more complex than anticipated. Egan takes seriously the hard problems of consciousness and identity that mind uploading would raise: Is a copy of you still you? What happens when you run multiple copies simultaneously? Can a simulation contain consciousness at all? The novel refuses easy answers, following its premises to disturbing conclusions. For readers who enjoy science fiction that engages seriously with philosophy and science rather than using futuristic settings for conventional plots, Permutation City represents the genre at its most intellectually ambitious.