When I last read Jingo, something like 20 years ago, I was unimpressed by it. As I started to re-read it, I didn't understand why, but by the end I did. It's muddled.
An island appears in the Circle Sea, claimed by both Ankh-Morpork and Klatch, threatining war. As assassination attempt is made on Klatch royalty in Ankh-Morpork, and Vimes needs to investigate this JFK-style crime. Political crime!
Except it then veers off over to Klatch, things get messy with thoughts on the police vs. soldiers, the nature of politics and war and crime and things, and then at the end the Patrician pops up as a deus ex machina to sort everything out. Fun threads get dropped, lots of the action doesn't actually seem to drive the story, and the resolutions were uninspiring.
It's still not a bad read - Pratchett knows how to keep a story spinning along - it just ended up feeling unsatisfactory. I can't remember if this was the last Discworld novel I read at the time, or just nearly the last one, but it didn't really inspire me to keep reading at the time. Returning to the series, I'll forgive this dud and keep going.