Dying wizard Drum Billet eagerly passes his magic staff on to a newborn wizard - the eighth son of an eighth son. Unfortunately, in his rush, he failed to notice the child was a girl. Unwittingly, Billet is responsible for the first ever female Wizard in Discworld.
All, including Granny Weatherwax (a witch) try to ignore the event, but neither the magic staff nor little girl Esk will let them.
Esk grows up amidst her brothers, but when she's nearly nine, a frightening incident involving Granny opens the flood gates to her magic abilities. Granny decides it is time to teach Esk to become a witch, in the hope that her wizardness can be squashed.
Of course, this proves impossible, and soon Granny and Esk need to embark on a journey to the Unseen University of Wizards. Esk finds that the chauvinistic wizards are unwilling to entertain the notion of a female wizard. But a nine-year old little girl and a cranky granny can be more than a determined handful ...
The character of Granny reappears in later Discworld books and she is an absolute delight: a stubborn witch with more that the average share of common sense - well, mostly anyway.
The genius of Pratchett is that you don't even notice how quickly you are willing to accept Discworld and its characters. Before you know it, this little cocoon of enchanting surreality is over.