My top 5, in no particular order: Orson Scott Card - Elements of Fiction: Characters & Viewpoint. Monica Wood - Elements of Fiction: Description. Orson Scott Card - How to Write Science Fiction. Rob Davis - Writing Dialogue and for Scripts. Gillian Robers - You Can Write a Mystery. I very highly recommend them, even if you don't want to write Sci-Fi or Mysteries. The advise they give is excellent.