One of UNESCO's jobs is to keep track of the books that get translated from one language to another. The latest UNESCO sum-up, for 1949, shows which U.S. authors of all time were doing the biggest translation business around the world that year. The leaders:
JACK LONDON43 separate translation editions (many of them in Russia and other Curtain countries).
JAMES FENIMORE COOPER30.
ERLE STANLEY GARDNER22....