This is the penultimate Vimes book, but the last one for me to read, due my admin error last time!It's good. Not quite as good as Snuff, but good nonetheless.
While the Watch series tend to cover social issues, this one is really just "two species with thousands of years of emnity, and Vimes trying to avoid the whole thing boiling over".
There was actually a lot less character development than I expected from reading Snuff. I was expecting both Willikins and the Summoning Dark to be rather more developed, as an interpolation, but most of the development seems to have landed in Snuff, glossed over by a few years of time passing.
Some themes from The Fifth Elephant are expanded on. "Devices" are introduced - apparently super-advanced technology from the dawn of time - but not yet heavily used. Feels like the set-up for future stories. The Watch finally gets a vampire. The novel moves things forward a little, but not a huge amount.
To my frustration, the finale of the book moves the action from Ankh-Morpork to the countryside again. I think this pattern is used to deprive Vimes of the ability to just call in a couple of hundred guards, and make him a little more of the individual superhero, but I wish he didn't get called out of the city quite so often!
All in, it's pretty good. It's not Snuff, but neither is it Jingo. A fun read.