I run hot and cold for Greg Egan. When he's good he's great, and when he's not he's a chore. I have to admit that it's entirely possible that whether I think he's good or not is entirely related to my ability to understand (or at least to think I understand) what he's talking about. This is possibly the hardest SF I've ever read - and I loved it!
The only downside for me was that he essentially turned an entirely new universe — one that not only did not run on the same laws of Physics as our universe, but apparently didn't even have a single set of physical laws — into the Game of Life
. I guess we could never really understand such a universe, but it seemed too simplistic.