Often portrayed as an odd amalgam of talent and lack of ambition, John Hay has confounded many attempts to delve his crowded, productive life. Hay enjoyed presenting himself as one who shied away from the limelight but was dragged into it by extraordinary gifts. His best friend, Henry Adams, helped to propagate this portrait. Yet the John Hay who appears in The Education of Henry Adams (1907), and in the diaries and correspondence that Adams helped to prepare for publication, does not square well with the historical record. As secretary of state under Presidents William McKinley and Theodore Roosevelt (1898-1905), Hay helped to usher in the "American Century," especially by enlarging the U.S. military and economic presence on the international scene. He also co-authored a biography of Abraham Lincoln that reached some one million readers and wrote many essays, poems, speeches, and short stories, as well as a...