When John Gawlor, a married advertising executive, is found dead alongside a teenage boy-hustler on Chicago's North Side, a police detective tries to figure out Gawlor's sexual identity--and first-novelist Cook alternates the cop's ponderings with a detailed, but relentlessly shallow, spot chronology of Gawlor's messedup sex life. 1952: Repressed teenager. 1956: Repressed college kid, impotent with a prostitute. 1957: Soldier in Europe, treated to oral sex by a lame German chanteuse. 1962: Husband of prim college sweetheart; abandoned sex with a bar pick-up. 1964: ""Across-the-desk sex"" and the joys of cunnilingus with a gorgeous colleague and, soon, with any white female in sight. 1968: A threesome. 1974: Black prostitutes. 1978: Sex with men, starting off with (by mistake) a transvestite--""It was. . . interesting. Hadn't he carried this prejudice quite long enough?"" Along the way, Gawlor's wife, though in the dark about most of this, tries to get her dour hubby to talk to a psychologist. But neither the shrink nor Cook ever comes close to explanations for Gawlor's restless obsession with sex. Perhaps that's because Cook wants Gawlor to function as some sort of Sexual Everyman of the Fifties, Sixties, and Seventies--becoming more depraved as our society goes sex-mad and liberated. But even an Everyman has to behave believably, and Gawlor doesn't; as a result, this is an intriguing idea (derivative of the film Carnal Knowledge) that, though handled with more seriousness than sleaziness, never graduates from prototype to character, from thesis to novel.