NYPD detective Jake Neuman, 54. left the force after his partner turned out to be a psycho-killer. (See Sweet Justice, which is summarized in detail here.) Now, however, he comes out of retirement--partly because things are edgy at home (wife Maria just bought a vibrator), partly because he's intrigued by two recent murders: the backstage shooting of rock-star Dimanche (a Madonna type), on the eve of her Broadway debut in a mystery-play; and the downtown shooting of the ""Nowhere Man,"" an early-morning jogger with no identification--and no friends or relatives, apparently, to notice his absence. Could the two killings be connected? Perhaps: the Nowhere Man is eventually identified as a computer-whiz and ruthless womanizer with a trendy life-style not unlike Dimanche's. Furthermore, two media-hustlers keep turning up through the two-track investigation: sexy filmmaker Nell Ward, who wants to make an NYPD documentary, but who (as the reader knows) has a dark secret life of drug-addiction and degradation; and smart-alecky tabloid columnist Terry Niles. So there'll be a strange crisscross of clues (lottery-ticket numbers, address-book names, answering-machine messages)--until Neuman winds up chasing a pair of crazed murderers around Shea Stadium (mid-game). Like the more shapely Sweet Justice, this is an implausibly contrived psychodrama, again hinging on dubious socio-sexual obsessions. Also, again, however, Oster's hip, sardonic, often free-associative narration is the main attraction, creating a noisy, densely evocative cityscape (from Sardi's to the E-Z Park Garage) with bravura dialogue, running gags, and telling urban details. In sum, then: police-procedural fiction chiefly for connoisseurs of style and tone, comparable to William Marshall's Yellowthread St. series.