Robert Dallek has previously given us two critically acclaimed biographies of Lyndon Johnson: Lone Star Rising and Flawed Giant. Now he chronicles yet another fractured luminary of American politics. In so doing, he delivers a remarkable cradle-to-grave account of JFK -- the best ever penned.

Dallek made the most of his hard-won access to generally embargoed family papers at the JFK Library -- a cache previously open to only a few Kennedy loyalists, notably Doris Kearns Goodwin. He also excavated much from the scattered archives of JFK's far-flung contemporaries, many of them unavailable when Goodwin's investigators did their work. (Unlike Goodwin, whose 1987 tome The Fitzgeralds and the Kennedys has been tainted by charges of plagiarism, Dallek refuses to delegate research tasks.)

Early in his book, Dallek smashes the canard that JFK was forced into political life following the wartime death of his elder brother, Joe. As Dallek shows, Kennedy absolutely lusted after public office. "I saw," Jack told a friend, "how ideally politics filled the Greek definition of happiness -- 'a full use of your powers along lines of excellence in a life-affording scope.' "

But first he had to get elected. Dallek details the precise mechanics by which family money was used to purchase the West Virginia primary in 1960. At the same time, he sheds new light on Jack's Russian-roulette mentality when it came to scandal. Example: JFK risked absolutely everything (not the least, his father's massive campaign investment) during the 1960 race when he invited an underaged cheerleader to his hotel room.

Throughout his book, Dallek quite appropriately portrays JFK as a gallant battler against such ailments as a congenitally bad back, colitis, and Addison's disease. Dallek likewise documents the various drug cocktails -- 10 to 12 medications daily, some addictive -- that he used and abused to remain on his feet: anti-spasmodics, muscle relaxants, phenobarbital, librium, codeine, demerol, methadone, novocain and procaine along with both oral and injected cortisone. He was also on doses of testosterone, and took nembutal for sleep.

The drugs sometimes had unintended consequences. During his first disastrous summit with Khrushchev, the drowsy, medicated JFK seemed to be struck dumb by the Soviet premier's many strident denunciations of capitalism. Underwhelmed by the apparently weak U.S. leader, Khrushchev came away from the summit inspired to new belligerence. Not long after, the Soviets built the Berlin Wall and positioned missiles in Cuba.

Dallek is especially adept at analyzing the key benchmark events, both positive and negative, that went so far to define the light and dark sides of Kennedy's truncated presidency. On the one hand, we have JFK's amateurish mishandling of the fiasco at the Bay of Pigs; on the other his calm, deliberate brinkmanship during the Cuban missile crisis.

Dallek goes on to argue convincingly that Kennedy did not plan to expand the U.S. role in Vietnam. And he lays bare the complex story behind JFK's often grudging and always dispassionate progress in civil rights.

Although Dallek finds much to admire in JFK, he does not fail to depict the man's contradictions. The Kennedy revealed here is both idealistic and fatalistic, ambitious yet self-destructive, blessed but doomed. Such is the eloquent and complex burden carried within An Unfinished Life -- Robert Dallek's extraordinary rendering of the brave, brilliant, but ultimately also incomplete JFK.

This article first appeared in the Providence Journal and is reprinted with permission of the author.