I think I figured it out now.

There are two writers named Greg Egan. One is a staunch humanist with a fine insight into the nature of the mind, but which unfortunately suffers from heavy depression. This writer wrote Permutation City, Diaspora and Zendegi.

The other Greg Egan really likes writing equations and figuring out how a planet would look if gravity was inside out, describe that in dizzyingly accurate detail, and just throw in a vaguely pro-science plot so that the whole endeavour is technically a "story" and not topological fanfiction. This Greg wrote the Arrows of Time trilogy, Dichronauts and now The Book of All Skies.

Don't get me wrong, I love a good description of a bridge. I'm just wondering what this Greg has done with the other one's body.