It's been years since the last one I read, so it's a bit hard to recall. But the stories that have really stuck in my mind are the results of Egan tweaking some physical law, constructing a universe that might reasonably arise under those physical conditions, and then writing a plausible adventure within that universe.
Dichronauts (2 spacial and 2 time-like dimensions instead of our 3 and 1) and the Orthogonal trilogy (Riemannian spacetime instead of our "Lorentzian") come to mind. I just really like the care he puts into constructing these universes, from how planets form (the worlds in Dichronauts are infinite hyperboloids instead of spheres), to how scientific discovery progresses (as a result of the physics in Orthogonal, light of different frequencies travel at different speeds and visually separate as a common matter of course, which leads to a much earlier understanding of relativity by a fairly primitive civilization). It feels like he's building universes from first principles and taking care to consider every little consequence and detail, which leads to a lot of "Ohhhhh" moments when you encounter something counter-intuitive but then realize it directly follows as a consequence of the initial physics tweak.
Dichronauts (2 spacial and 2 time-like dimensions instead of our 3 and 1) and the Orthogonal trilogy (Riemannian spacetime instead of our "Lorentzian") come to mind. I just really like the care he puts into constructing these universes, from how planets form (the worlds in Dichronauts are infinite hyperboloids instead of spheres), to how scientific discovery progresses (as a result of the physics in Orthogonal, light of different frequencies travel at different speeds and visually separate as a common matter of course, which leads to a much earlier understanding of relativity by a fairly primitive civilization). It feels like he's building universes from first principles and taking care to consider every little consequence and detail, which leads to a lot of "Ohhhhh" moments when you encounter something counter-intuitive but then realize it directly follows as a consequence of the initial physics tweak.