Permutation City is a science fiction novel written by Greg Egan. The story takes place in a future where people can create digital copies of themselves and live in simulated worlds known as 'Autoverse.' The protagonist, Paul Durham, is a software engineer who becomes obsessed with creating a perfect copy of himself. As he delves deeper into the nature of consciousness and the ethics of digital existence, Paul's reality begins to unravel. Permutation City is a mind-bending and philosophical exploration of identity and the nature of existence.