What I realized, reading the lush and gorgeous prose of McKillip's story, is that great fantasy will transcend the bounds of genre and go somewhere that's difficult to label or define; and that excellent writing can be found in small packages. This isn't an incredibly long book, but like poetry, so much is condensed into a small space that you can turn to almost any page and find word-images so vivid you can almost taste them:
Winds shook me apart piecemeal, flung a bone here, a bone there. My eyes became snow, my hair turned to ice; I heard it chime against my shoulders like wind-blown glass. If I spoke, words would fall from me like snow, pour out of me like black wind.
The mysterious journey of Rois Melior into the secrets of the mysterious Corbet Lynn parallels her journeys into the heart of the surrounding woods and into her own knowledge of self. The journeys weave together eerily, seamlessly, until one is inseparable from the next and none has meaning without the others. In the end, to me, it resembled less a fantasy novel, and more a work of magical realism along the lines of Marquez or Rushdie.
It leaves you with questions at the end, and not many answers; if you like your fantasy straightforward and clearly narrative, it might not be for you. But if you harbor a secret wordlust for poetic turns of phrase, if you're willing to read something that blurs the boundaries of dream and reality and leaves it up to you to decide which is which, give it a try.