On October 24th, Nicholas Gage signed copies of his new book, “Greek Fire: The Story of Maria Callas and Aristotle Onassis,” at a party hosted by Lucky Roosevelt at her Georgetown home. The author, a former investigative reporter for The New York Times, reveals startling new information about the couple in his book, tracing their stormy relationship from their first meeting at a 1957 masked ball in Venice to the end of their lives. Gage was able to gain access to some of Ms. Callas’ most private papers, providing a new view of her personal life.