Terry Pratchett takes Shakespeare's Macbeth and then turns it up till the knob comes off. It's all there - a wicked duke and duchess, the ghost of the murdered king, dim soldiers, strolling players, a land in peril. And who stands between the kingdom and destruction? Three witches. Granny Weatherwax (intolerant, self-opinionated, powerful), Nanny Ogg (down to earth, vulgar) and Magrat Garlick (naïve, fond of occult jewellery and bunnies).