If a friend hadn't been commanding officer, Harry Truman's poor eyesight would have barred him from the Army; if the Pendergast machine hadn't supported him for the nomination, he wouldn't have been county judge, district judge, or U.S. Senator; if the other prospects hadn't had handicaps, he wouldn't have been tagged as Roosevelt's running mate. But if he hadn't become a popular leader in the Army, a respected administrator as judge, a household name and his own man as head of the Truman Committee, he would never have become President, even by accident--as this latest, leanest biography demonstrates so well, along with his lifelong loyalty. Initially he is presented as ""the man who ordered the bomb dropped"" (and didn't regret it); subsequently the crises and accomplishments of his administration are set forth in sufficient detail for the young reader to whom this is history. (This is one of the few biographies of a president that does devote adequate space--about two-fifths here--to his presidency.) Mr. Hayman has resisted the temptation to sprinkle his narrative with outrageous anecdotes or launch it with small talk; it's an example of how to write young biography without writing down, of how to simplify without being simplistic.