Gardens of the Moon (and sequels) by Steven Erikson: These books will appeal to fans of G R R Martin and lovers of complex, gritty, military fantasies.
The Ladies of Grace Adieu by Susanna Clarke: These short stories will be treasured by lovers of fairy tales and eighteenth-century England.
Little, Big by John Crowley: Perfect for lovers of beautiful language, dreamlike stories, and subtle magics.
The Player of Games (and all the Culture novels) by Iain M. Banks: Just the things for science fiction fans who like grand ideas and witty writing.
Night of the Living Trekkies by Kevin David Anderson: The logical choice for trekkies looking for a laugh.
The Collected Stories of Lydia Davis by Lydia Davis: Perfect for the serious reader of interesting fiction.
Spun by Sorcery (and the sequels) -- Barbara Bretton: For the geeky knitter or the sewing S/F fan this is perfect fit.
Buddha by Karen Armstrong: Perfect for students of religious history and those wanting a clear and balanced account of the Buddha.
The Long Ships by Frans Bengtsson: Perfect for the fan of historical fiction, nautical adventures, and, well, Vikings, and anyone who reads to be transported to a foreign place and time.