Dark fantasy often takes place at night, among creatures of the night. The tone is often cynical, the heroes Byronic. The difference between dark fantasy and horror are several. Horror exists to evoke fear, as constantly as possible. The moods of dark fantasy are many, and include a pleasant sort of wonder. In horror, the creatures of the night must be fought and overcome by the protagonists; in dark fantasy, they may BE the protagonists, as sympathetic as you like. Dracula is horror. Dark Shadows is dark fantasy.

• Beowulf, one of the first great dark fantasies of all, tiptoeing pretty close to horror
• Flesh and Spirit and Breath and Bone by Carol Berg
• Grendel by John Gardner, retelling Beowulf from the monster's point of view
• Those Who Hunt the Night and Traveling with the Dead by Barbara Hambly
• Conjure Wife by Fritz Leiber
• Interview with the Vampire, The Vampire Lestat, Queen of the Damned, The Body Thief, The Vampire Armand, The Mummy, or Ramses the Damned, The Witches of Mayfair, Taltos and others by Anne Rice
• The Dracula Tapes, An Old Friend of the Family and Thorn by Fred Saberhagen
• These and all the other St. Germain and Olivia novels by Chelsea Quinn Yarborough:
  

  Le Comte de Saint-Germain
  Mansions of Darkness
  Writ in Blood
  Darker Jewels
  Better in the Dark
  Blood Roses
  A Candle for D'Artagnan

You can buy Dark Fantasy titles through the Other Worlds Bookstore.