Sourcery

"Once upon a time, there was an eighth son of an eighth son who was, of course, a wizard. As if that wasn't complicated enough, said wizard then had seven sons. And then he had an eighth son - a wizard squared (that's all the math, really) - who, of course, was a source of magic, a sourcerer. Unseen University, the most magical establishment on the Discworld, has finally got its wish: the emergence of a wizard more powerful than they've ever seen. But be careful what you wish for . . . As the drastic consequences of sourcery begin to unfold, it's up to one unlikely wizard to save them. Rincewind has survived a string of misadventures, including falling off the edge of the world - which is no mean feat when it's flying through space on the back of a turtle and held up by four elephants. Now, he must take the University's most precious artifact, the very embodiment of magic itself, and deliver it halfway across the Disc to prevent a mathematically blessed sourcerer from leading the wizards to dominate all of Discworld. Can Rincewind and his tiny band, including the carnivorous Luggage, stave off the Apocalypse? The Discworld novels can be read in any order but Sourcery is the 3rd installment in the Wizards series and the 5th Discworld book"--