Of all the Discworld books, the ones about Tiffany Aching are my favourite. They are marketed as Pratchett's books for children, but I think that is doing them a disservice. Why should they be savoured only by children? They would be wasted.
This is the best of his books so far, in my opinion.
Tiffany is establishing herself in her role as witch of the chalk. In this book she is required to defend her reputation, not only as a witch, but as a witch of her own steading. She must fight the man with no eyes, the man sent to hunt her down over the centuries, with nothing in his heart but hatred for witches, and she must find true love, deliver twins and not forget to dress Brian's mum's sore leg.
Pratchett has gone from strength to strength over the years, and has become increasingly philosophical, without losing any of his cheekiness, lightness of touch and ear for a good joke. In the character of Tiffany he seems to be exploring what it means to be human, and humane. What it means to take your place on the earth and be a part of a community. In this book he deals with the passing of life, the fear of otherness and the shouldering of personal responsibility, but never loses his ability to tell a crackingly good story that will keep you turning the pages and feeling sorry when it's over.