The new McKillip novel is Alphabet of Thorns. It's quite good, but I'm not sure what I can say about it without a spoiler warning, even a mild one, since exactly who the protagonists are isn't entirely obvious from the get-go.

I can write a bit about it in a cut-tagged entry if you like. :)

Have you read In the Forests of Sere? It is also quite good (and not as easy to spoil).