Honestly, I am not sure who I'm recommending this to, other than anyone, everyone, who hasn't read it. While it is a retelling of a famous story, it's a retelling in the loosest terms. Yet as I reread it recently, I couldn't help but notice how much fairy tale tropery Pratchett uses--and turns on his head.
For lovers of fantasy and folklore, you could do a lot worse than to pick up a Discworld novel, and this is a great starting place. If you're not familiar with the series, the first book is The Colour of Magic. However, the series is made of subseries, and Wyrd Sisters is the first one featuring my favorite character, Granny Weatherwax, an extraordinary witch and headologist.
Plus: Macbeth! Shakespeare! And other fairy tale references.