I have read Iron Council, the Scar and Perdio St station.
The city reminds me of an eighteenth century Edinburgh. A sort of University town yet with deep conservative elements. I found the detail to be the most fascinating thing about these books, I think I've said before I'm a detail junkie, things everyone else finds boring I kinda love!
They take some reading but the Scar is better to get into as other posters have said it's a more polished book. Iron Council though was a slog which once things got going was un putdownable, but percivere it's a hard read!