I'm probably not doing this book justice with my rating, but as much as I think the writing is brilliant, it dragged for me badly.
I started it thinking it would work for my werewolf square in bingo, and by the time I realised it definitely wasn't (Agula the werewolf is only mentioned and never appears), it was too far in to stop.
This is a much deeper, more serious storyline that any of the other Discworld books I've read so far and there's a lot of political philosophy (and a fair amount of quantum physics). It's brilliant political philosophy, but I was expecting werewolves, so Poli-Phi and string theory was more work than I was prepared for. (Also, I'm not a fan of time travel plots.)
Still, this is Pratchett and as MT said, for a book I was complaining was hard work to get through, I was laughing out loud an awful lot. Pratchett is a genius at using his words, and the scene involving the ox and the raw ginger had tears coming to my eyes (and likely theirs). So many laugh out loud moments in this one that even though I'm glad it's over, I'm definitely also glad I've read it.
(Luckily, there are enough other elements in this book that I can use it for the Free Space.)