By Dennis Drabelle, The Washington Post Has a great mystery writer ever gone about her craft more self-consciously than P.D. James? She demonstrated her familiarity with the genre not only in her study “Talking About Detective Fiction” (2009) but also in references to predecessors and conventions sprinkled throughout her own fiction. In “The Mistletoe Murder,” her first and presumably only story collection (James died two years ago, at the age of 94), a nod goes to the woman often called the best-selling mystery writer of all time.