BOOK REVIEW / How a Boston-Irish boy became St Jack . . .: JFK: The Life and Death of an American President. Vol 1: Reckless Youth - Nigel Hamilton:, Century, pounds 20

NO LEGEND is more bewitching than the legend of Jack Kennedy. Seldom has a romantic myth of so little substance gripped a nation's imagination so firmly, or been re-told so frequently, or with greater indifference to the reality.

The facts themselves are mundane. John F Kennedy was a wealthy young American politician of little distinction who (like Bill Clinton) won the Presidency largely by default after a long period of lacklustre Republican rule. His brief administration was notable mainly for an ill-advised invasion at the Bay of Pigs and a scary gamble with nuclear weapons during the Cuban Missile Crisis. There were no major domestic achievements. The blurb to Nigel Hamilton's book calls Kennedy 'this century's most popular and charismatic American president'. In fact, in terms of votes obtained at an election, he was one of the least popular. If he'd been ugly, or had lived to be old, he would also be one of the least known - a sort of American Bonar Law.

It was the glamour of the Kennedy court, the style, the money, but above all the theatrical public killing that turned the name of Kennedy into a deified Caesar immune from the depredations of mere historians, or of witnesses who wanted to put the record straight. So far from tarnishing the image, revelations of JFK as a philanderer seem almost to have enhanced it. Certainly, they have done little to discourage presidential hopefuls from seeking to assume the Kennedy mantle. Clinton has just coolly blasphemed his way to office, invoking not just the name but the mannerisms, rhetoric, perhaps even the coiffure.

But the question remains, as Nigel Hamilton puts it: 'Who really was John F Kennedy behind the winsome, orthodontically perfect smile?' His answer is this carefully researched biography, a forensic though also admiring work which deftly analyses all aspects of Kennedy's background.

An important part of the Kennedy legend was the notion of the clan as a happy family infused with bog-Irish warmth. Hamilton deals with that one ruthlessly. Making use of a marvellous cache of previously undiscovered letters from Jack to a boyhood friend, Lem Billings, he sketches out a bleak picture of private horror and pretence. Joe Kennedy - Jack's father, and founder of the family fortunes - appears as part-crook, part political fantasist and part old goat, who when not ludicrously plotting to displace Roosevelt as US President was trying to bribe his sons' girlfriends to sleep with him. Jack's mother Rose has been presented as saintly earth mother and dedicated materfamilias; here she appears as a miserable and repressed social climber who imposed an icy discipline upon her children, retreated from her husband's maltreatment into the rituals of her faith, and tacitly condoned the dreadful decision to lobotomise their retarded daughter Rosemary as a means of curbing her rebellious behaviour.

Thus - in Hamilton's view - it was not an abundance of love but the opposite that provided the motor to Kennedy aspiration. Having acquired money by dubious means, Joe attempted to use it to buy his way into smart Boston society. He encountered, however, a brick wall of anti-Irish ethnic prejudice, which his own reputation as a shady operator did not help. As a result, his children grew up in an atmosphere of 'social quarantine' and, Hamilton speculates, had a strong urge to prove themselves.

In Jack's case, there was yet another factor: physical illness. Hamilton meticulously unravels the details of a series of ailments that dogged the future President from his chidhood. Photos of him show a delicate, emaciated teenager with wide eyes, protruding nose and nervous smile. Many months were spent recovering, as much from courses of medical treatment as from the conditions they were supposed to cure. On one occasion, leukemia was incorrectly diagnosed. There followed a bout of pokings and scrapings by expensive doctors. As soon as he regained his strength, Jack took his revenge by trying to seduce the nurses. 'The girls are few and far between,' he wrote from a convalescent home in Palm Beach, 'but speaking of between, I expect I shall get laid shortly.'

Getting laid became a major preoccupation. 'What he wanted was fun,' says Hamilton, and despite or because of his illnesses he usually got it. There was also, though, a bookish, even intellectual, streak. Jack's elder brother Joe - killed on a flying mission in the Second World War - had it too, and studied under Harold Laski at the London School of Economics. Jack was less earnest, and roamed restlessly around Europe, liking England best, partly because of the debutantes. He made use of his father's base as American ambassador in London to write a book, Why England Slept, which turned him into a minor celebrity.

Hamilton shows that, despite FBI suspicions that Jack's Danish mistress was a German agent, he had a good war. He gives an interesting account of the naval operation in the Pacific that turned Jack into a national hero. Following a ramming by a Japanese destroyer, young Kennedy - in a kind of Chappaquiddick in reverse - swam for help, saving the lives of his men at great risk to himself. The episode had the incidental advantage of equipping him, in the eyes of would-be backers, for a political career.

As the author reminds us, the most important backer was his own rich and unscrupulous father, who - frustrated in his own ambitions - was largely responsible for bribing, buying and bullying his son's way into Congress at the unusually young age of 29. Hamilton concludes this volume with the observation that, in spite of everything, the budding politician had escaped his father's 'narrow, selfish Boston-Irish bigotry and found a pluralist, idealistic, and yet internationally committed liberalism'. There is little evidence of self-sufficiency here, however, and we must await Volume Two for convincing proof.

(Photographs omitted)