The Deuticke publishing house said yesterday that Morton died overnight in his Vienna hotel room.
Morton wrote 12 books including "The Rothschilds" and "A Nervous Splendor," both of them National Book Award finalists.
"The Rothschilds" was made into Tony Award-winning musical, while "A Nervous Splendor," chronicling 1888 to 1889 in Vienna, focused on the major Austrian personalities and events of that year among them the birth of Adolph Hitler, whose rise to power led to Morton's self-exile 40 years later.
Morton was born Fritz Mandelbaum in Vienna on October 5, 1924. He and his family fled first to London then to New York a year after Hitler's 1938 annexation of Austria.