Oh, Feet of Clay is the one with the golems and someone poisons Vetinari which Vimes takes as a personal insult. It's really good - though of course I say that about practically every Terry Pratchett book :D

My favourite bit is probably troll Constable Detritus's interrogation technique. Just an almost throwaway few lines, but it always makes me smile. But I won't spoil it here :D