No other writer knew him as I did,"" says Nolan of his relationship with the late movie-star Steve McQueen. And this new biography (Nolan did a juvenile McQueen bio in 1972) is chock-a-block with quotes from McQueen--some of which sound like the real McCoy, some of which don't. (While collaborating on an unfinished autobiography, ""Steve had told me many things, talked at length of all he had been and done. . . ."") But, despite all such insider claims, the personal story here remains flat and sketchy--while much of this dullish book is given over to moviemaking details (stuntwork especially), facts-and-figures from McQueen's racing-hobby careers, and second-hand press-release/gossip-column material. Deserted by his father, unloved by his mother, young Steve wound up in reform-school--where he acquired ""a sense of self-worth."" Then: five years of wandering and Marine service (his ""moral values were highly questionable at this stage""), casually-begun acting studies in N.Y.--and a slow, steady theater/film/TV career that peaked with Wanted, Dead or Alive . . . and led to ""the status of instant sex idol"" with The Great Escape. Meanwhile, there was marriage to dancer-actress Neile--who became increasingly unhappy over McQueen's obsession with motorcycles, race-cars, and other risk-taking ventures. Marriage #2--to All MacGraw--failed too. ""Bored and rootless, uncertain of what career goals to pursue, and angry over his eroding marriage, Steve began to drink heavily. He was also smoking again. . . ."" And after the utter failure of an attempt at serious acting--in Ibsen's Enemy of the People--there was a final obsession with biplane-piloting (associated with his lost father), then lung cancer: the last chapter is devoted to the ""first full account"" of McQueen's unorthodox cancer treatments (about which Nolan is shrilly defensive, with lashings-out at the medical establishment). Only for undemanding fans, then--especially those who share the McQueen/Nolan passion for cycles and sports-cars.