Pratchett finally (in this sixth book in the Discworld series) reels back the disaster level: it's not the entire world that's under threat, it's just the kingdom of Lancre. Happily, this is where Granny Weatherwax lives - one of Pratchett's better characters. And he also introduces Nanny Ogg, another entertaining witch. And to better make them conform to the Shakespearean ideal that he parodies throughout the book, there's a third witch - Magrat Garlick. We start with one of them screeching "When shall we three meet again?!" followed by a much more normal tone from one of the others expressing how impressed they were with the quality of the screeching. So lots of Macbeth going on there. But Pratchett drags in jokes from King Lear, Romeo and Juliet, and very likely several others I missed. And then there's Hwel, the playwright, who channels Laurel and Hardy, the Marx Brothers, and a variety of other acts from our world that make no sense on the Disc.
The book starts with the king of Lancre dying. This may have been caused by the tumble down stairs, but more likely it was the knife between the shoulder blades. While the witches regard this as a perfectly normal process of succession, they aren't impressed with the behaviour of the new king and they also discover that the entire kingdom (which turns out to have a personality of its own) doesn't like him at all. And so they get involved in politics.
He goes to a lot of trouble with the Shakespeare parodies, and yet I didn't find them particularly funny. Despite this, I actually quite liked the book: the story was a bit more structured than the previous ones, and when he stayed away from Shakespeare it was actually one of the funniest things he's done.