In the new book, "Back Channel to Cuba: The Hidden History of Negotiations between Washington and Havana," authors Peter Kornbluh and William LeoGrande use recently declassified documents to expose the secret history of dialogue between the United States and Cuba. Among the revelations are details of how then-U.S. Secretary of State Henry Kissinger considered launching airstrikes against Cuba after Fidel Castro sent troops to support independence fighters in Angola in 1976. In the years that followed, top-secret U.S. emissaries, including former President Jimmy Carter and Nobel Prize-winning author Gabriel García Márquez, worked to normalize relations with Cuba. The book's release comes as Cuban leader Raúl Castro is set to participate for the first time in next year's Summit of the Americas in Panama. Cuba recently denounced the Obama administration for extending the more than 50-year embargo for another year in a little-noticed move in September.