Been a huge fan since I came across his short story Crystal Nights in a collection. Zendigi gave me the creeps bad, because it was just all too realistic.
Schild's Ladder about melted my brain, because I couldn't get it out of my head that the last third or so was a virtual construct written in the fabric of clashing universes. Also, I just can not buy that humanity as a whole would adopt puzzle-peice genitals.
That said, he is amazing, and if you want to read Schild's Ladder, his short story Singleton should probably be read first, as it helps set the framework for what the hell is up with Quisps. Hey, here's a link!
http://gregegan.customer.netspace.net.au/MISC/SINGLETON/Singleton.htmlEgan is probably about on par with Neal Stephenson for having books that can double as IQ tests.