Shadowmarch — Tad Williams

The first Marchlands kingdom, Southmarch (commonly called “Shadowmarch”), lies directly on the edge of the mysterious Shadowline, a shroud of endless mist that marks the entrance to the realm of the fairy-folk, the Qar. Crossing the Shadowline is said to drive any human mad, but, as far as anyone knows, the line has not moved any further south for centuries. Now, inexplicably, it has begun to creep slowly but surely deeper into the lands of Southmarch, bringing an unknown menace with it.

Coupled together with this threat is the dissension and endless political maneuvering of many of Southmarch's nobles. The king of Southmarch has been captured and is imprisoned in a distant land, and when the prince regent is murdered, the burden of rule falls to the inexperienced princess, Briony, and her moody brother, Barrick. Faced with invasion, betrayal, and conniving nobles seeking to take advantage, it is up to them alone to hold Southmarch together.