Permutation City is smart and delightful, and messes with the reader’s mind. This novel of virtual reality with multiple levels of simulated word is an example of great world-building.
1. Start with basic science.
2. Change a few principles and laws to create pseudo-science.
3. Build a world based on this new pseudo-science.
Greg Egan creates the new world by laying down the new principles and laws, and challenges the reader to take the journey into the unknown. As a result, he gives credit to science and makes pseudo-science a key character in the story, rather than just using some fantastic science as the background, or as an excuse to a story that could happen in many other settings.