Two years of research in the Kennedy Library and more than 150 interviews--many of them excerpted here--yield a singularly close and utterly fascinating account of JFK from prep-school graduation to Congressional debut. In disengaging man from myth, the authors concentrate on Kennedy's health, his women, and his naval career (Clay Blair is a naval historian, novelist, and former SEP editor). An elaborate reconstruction of the PT-109 episode leads to the conclusion that Kennedy performed some heroic acts and some rash ones, and--like the crew--felt himself disgraced by the loss of the boat. The PT legend was largely the creation of a New Yorker piece by John Hersey, husband of his lost perhaps-love Frances Ann Cannon. There was also a long affair with Inga Arvad, a stunning columnist and suspected Nazi spy, which probably drew FBI attention during Kennedy's naval intelligence stint and may have landed in Hoover's presidential blackmail files. Emotional reserve and a liking for movie-and-milkshake dates marked his many other liaisons with beautiful and witty women. JFK's back, say the Blairs, was a problem from birth, not the result of a football or WW II injury; and in 1947--after a vigorous freshman year in Congress--he was diagnosed as having Addison's disease. Since the disease was often fatal at the time, the ambitious Kennedy family covered up the diagnosis; but the authors attribute JFK's subsequent absenteeism and lackluster performance to this circumstance. Whatever the ultimate accuracy of the book's conclusions, it gives a rich sense of Kennedy's combination of shyness, sensitivity, and callousness; his deliberate use of what he called his ""BP--Big Personality""; and the disabilities of having a spectacularly amoral father, A revelation surprisingly free of malice or prurience.