Snow White and Rose Red / Patricia C. Wrede.

In this romantic version of the classic fairy tale, Snow White and Rose Red live on the edge of the forest that conceals the elusive border of Faerie. They know enough about Faerie lands and mortal magic to be concerned when they find two human sorcerers setting spells near the border. And when the kindly, intelligent black bear wanders into their cottage some months later, they realize the connection between his plight and the sorcery they saw in the forest.