I don't remember which I encountered first: Helene Hanff's book, 84 Charing Cross Road, or the Anne Bancroft / Anthony Hopkins movie of the same name. All I know is that decades later the title's blend of London, letters, and books still enchants me.   Published 50 years ago, 84 Charing Cross Road is a romance of the mail—a collection of letters between Helene, a feisty New York writer, and Frank Doel, the unfailingly polite manager of an antiquarian London bookshop. Individually, those letters speak of books and the correspondents' day-to-day lives. Collectively, they weave together a mee