Have you read his Bleeding London? I've been meaning to read that forever (and moved it like 4 times). I think I'll finally get to it this spring.
I'm also taking a bit of break from the serious stuff and am reading Lauren Beukes' Zoo City, which is sort of a future fantasy novel where people who commit terrible crimes are paired up with animal familiars -- and are then ostracized. It is notable mostly for being set in Hillbrow, South Africa. The set-up is hard to swallow, but it moves along quickly.
Looking at a list of his novels, it appears that the only one I've read is A Knot Garden. I enjoyed that one much more than The City Under the Skin. The City Under the Skin has a cartoon-like quality to it which doesn't appeal to me.