Each working day from January 29 to November 1, 1951, John Steinbeck warmed up to the work of writing East of Eden with a letter to the late Pascal Covici, his friend and editor at The Viking Press. It was his way, he said, of 'getting my mental arm in shape to pitch a good game.'Steinbeck's letters were written on the left-hand pages of a notebook in which the facing pages would be filled with the test of East of Eden. They touched on many subjects-story arguments, trial flights of worknamship,