The second in the His dark materials series (see the previously reviewed Northern Lights aka The Golden Compass), Subtle knife is a stunning moving read mixing some of the familiar characters of the first novel with some new (soon to become familiar) ones.
Lyra on the run from her world at the end of Northern Lights finds herself catapulted into a new one, meanwhile young Will desperate to save his mother from the mysterious men who are following her accidentally finds himself in a strange other world in the city of Cittagazze, a strange town that appears to be run entirely by children. On a quest to find his explorer father, his and Lyra's missions unexpectedly collide as the novel moves between Lyra's world, Earth, and this odd new realm.
Knife has all the adventure of the earlier volume, but it's also a rather more grown-up read. Both Lyra and Will are forced to grow-up rather sooner than expected by the events that befall them, so it manages to be both a fantasy adventure, and an, at times moving, coming of age tale.
I loved this novel. It was so beautifully written. And for any adult who has mocked reading children's stories, I would advise them to start here. It may be marketed towards a younger audience, but it is a curiously grown-up story. Wonderful writing, beautiful, moving book. Children's fiction at its very very best.