Darwath by Barbara Hambly
The Darwath Series is an epic adventure that begins with the rising of the Dark, a force of chaos that brings a civilization to its knees. Barbara throws in two characters that enable her to spell out the political and physical landscape while drawing you into her story.
The author is a deft hand at painting you a believable world with very few strokes and drawing imperfect characters you want to know more about. Highly recommended.