Wyrd Sisters, by Terry Pratchett, 1980

A Discworld sendup of Macbeth that quickly takes on a life of its own. Granny Weatherwax, Nanny Ogg, and Magrat Garlick are Macbeth's own witches brought into hilarious relief, and characters I'll not soon forget. Satiric adult fantasy, safe for young readers with the faint exception of some subtle and naughty winks at, er, Nature. Most desperately recommended!