I loved reading this book. It was the book Jingo should have been - international politics in a Discworld setting, with Vimes.
Unlike Jingo, almost all the action takes place abroad from Ankh-Morpork - this time in Uberwald, a land of werewolves, vampires, dwarves and some humans. There's political intrigue and a bit of detective work, and it all hangs together pretty well. I won't spoil the plot, but I enjoyed it immensely.
It's interesting to see Vimes as an element of Ankh-Morporkian cultural imperialism. People in Uberwald resent the drain of their folk to Ankh-Morpork, and how they break tradition there, and then Vimes turns up to the dwarves with a troll (who they're at war with) and a visibly female dwarf (going against millennia of tradition), and his attitude is simply "this is what we do in Ankh-Morpork, deal with it". Then he rails against the laws of Uberwald, whilst being there. Lucky he's a diplomat, I guess.
As with all Discworld novels, it's an askew take on the round world. The political goal is to ensure Ankh-Morpork gets a good deal on products from the dwarves' fat mines, which sounds ridiculous until you think of the wars we've had over oil.
I particularly enjoyed the introduction of the "clacks" in this book. By the start of this novel, telegraphy has sprung up. It's now just a thing they have, without too much fanfare, which is a pretty neat way of introducing a Big New Thing to the Discworld. It's also part of how Terry is changing the world. A generic fantasy world seems stuck in stasis. Indeed, many of the early Discworld books can be read in any order, there's little sense of the world progressing. Indeed, some of the books are like the Discworld's immune system rejecting alien concepts that push the world towards round world equivalence - e.g. Moving Pictures, Soul Music.
That changes with the Watch sequence. The Watch clearly evolves over a few books into a modern police force, and it feels like a catalyst to allow Terry to evolve the whole world, bringing in things like the clacks. And somehow this feels right. It is a world on the cusp of change. Just like our own world during the industrial revolution, there was a sudden change from a world that looked a bit like a fantasy novel without magic to our modern world. Bringing this to the Discworld is fascinating.