Lyra's Oxford
A charming little book, lavishly produced with tuck-in maps, a simulated Baedecker's page for an imaginary Oxford, and random postcards from unexplained (and inexplicable, but intriguing) people.
The trick of interesting artifactual fiction is to avoid explaining too much. I've entered Pullman's world in the middle of the performance, and the effect may be exaggerated for me, but I found the lack of explanation a delightful change from, say, Harry Potter.