How can any series not be stale after 24 volumes? I think TP wants to concentrate on one subset, probably the Witches books [although the City Watch books picked up after this]. Vimes is such a good character though that he leads the narrative on. Apart from him, T5E is a bit like Carpe Jugulum all over again: one of the groups of not quite human predators (vampires in CJ, werewolves in T5E) decides to shift its predations up a notch. Igor makes an appearance again and we're told a lot about dwarfs and their way of life, including their sexual dimorphism, which only occurs when it's needed.