THROUGH most of his nearly eight years as President, Harry Truman was profoundly unpopular. Joe Martin, the Republican Speaker of the House in the late 1940's, called Truman "the worst President in history." Liberals so despaired of him during his first term that they tried to draft Dwight D. Eisenhower to replace him as the Democratic nominee in 1948. Even among the many who liked Truman personally, there was always a tendency to view him as one member of the Cabinet did on April 12, 1945, the day Franklin Roosevelt died. Truman was sitting alone in a big leather chair against a wall in the Cabinet Room of the White House, waiting for the Chief Justice to arrive and swear him in as President. The Cabinet member glanced at him and later remembered thinking: "He looks like such a little man."

Truman's popularity revived at times during his Presidency, most notably during his remarkable campaign for re-election in 1948. But the revivals were always brief. The real rehabilitation of his reputation -- the process that has turned him into something of a folk hero -- began later, well after he left office, and has accelerated in the 20 years since his death. Its culmination may be "Truman," David McCullough's warm, affectionate and thoroughly captivating biography. "Truman," Mr. McCullough writes near the end of this long book, "held to the old guidelines: work hard, do your best, speak the truth, assume no airs, trust in God, have no fear." He was "a figure of world stature, both a great and good man, and a great American President." . . .

No brief review can begin to do justice either to Truman or to the monumentally persuasive job McCullough has done re-creating his life and times.