Simply the best SF I've read in a long, long, time, this is a top piece of magical-realist world-building from one of the top ideas men in British Science Fiction.
Set on a terraformed Mars and drawing on everything from Edgar Rice Burroughs to the flavour of the month in physics, string theory, the overwhelming feeling is of the planetary romances of later Jack Vance. There are wacky religions, giant steam trains, a bunch of government-licensed pranksters who humiliate threats to the status quo, and one of the strongest female heroes ever written by a man.
Buy this one, it doesn't dissapoint on any level. Excellent.