Wyrd Sisters

The three witches join forces against an evil king, while the Discworld sees the rise of a superb actor and a dwarf playwright. First appearances of Nanny Ogg and Magrat Garlick.

This was the first thoroughly good Discworld book, and remains one of the best of them, written back when Pratchett was really funny; although, reading it again now, I see that he had some tendency to moralize even then.

Not high literature of course, but a good story and good fun, with assorted references to drama through the ages, Shakespeare in particular.