I'm a diehard Pratchett fan and I really think the Tiffany Aching series is where he shines. This is a really great introduction to the series. Set on the Discworld but removed from a lot of the over-the-topness of the main series books, this follows Tiffany, a nine year old would be witch, as she sets out to get her brother back from the queen of the fairies. The main plot is carried and deepened as Tiffany remembers stories of her grandmother, who was definitely not a witch, Granny Aching that help her reckon with the world around her and human nature.