Equal Rites — Terry Pratchett

"THERE'S NO SUCH TIHING AS A FEMALE WIZARD!"

But on the Discworld, a flat realm carried by four elephants riding on the back of a giant turtle, there's also no such thing as impossible. And so, a wizard on the brink of death tries to pass on his staff and powers to an eighth son of an eighth son who is just at that moment being born in the little town of Bad Ass. The fact that the son is actually a daughter is discovered just a little too late.

Granny Weatherwax, the town witch, insists on turning Eskarina into a perfectly normal witch, thus mending the magical damage of the wizard's mistake. But the wizard's staff has a whole different future in mind for Esk--a future which requires the young female wizard/witch to penetrate the inner sanctum of the Unseen University. Having accomplished this, she can then attempt to save the world with one well-placed kick in some enchanted shins....