This tale of Discworld follows shortly after Lords and Ladies
and takes Granny Weatherwax and Nanny Ogg to Anhk-Morpork (Magrat Garlick
is now a Queen rather than a Witch, and is therefore otherwise occupied).
They are in pursuit of two things: Agnes (Perdita) Nitt, who might just
succeed Magrat as one of the local witches; and the publisher of Nanny’s
cookbook (a collection of dishes with aphrodisiac properties) which has
sold thousands of copies with virtually no recompense to Nanny. But
that’s only what the book’s about; it’s not what the book is.

And what the book is, is a parody of that great Broadway Smash of the
1990’s, Andrew Lloyd Weber’s most overblown production, Phantom of the
Opera, a show which I have seen and which I personally cannot abide.
(I might perhaps expand on that at a later time). Few of Pratchett’s
books are so narrowly targetted as this one, but it’s very well done,
with lots of excellent bits and wonderful lines; plus there are some
walk-ons from some of the usual Ankh-Morpork suspects. The opera will
never be the same.