Two children, after their divorced mother's death, must go to live with their aloof, decadent, virtual-stranger of a father: a fair notion for a 200-page YA novel, but stretched out here--with some graphic sex and acres of talk--to a shrill soap-opera nearly twice that long. When terminally-ill novelist Catherine Emerson commits suicide, she leaves instructions that twelve-year-old Maddie and ten-year-old Jason are to live with their father, disco-trendy photographer David Fredericks. . . even though Catherine hated him (for good reasons). Maddie is hostile, blaming Fredericks for her mother's death. Jason is terrified. And their father hardly seems eager: his latest live-in girlfriend shows up to collect the kids from Naomi Rappaport (a lawyer for the late Catherine's publisher), saying ""I want them. David has agreed to try it out, for my sake."" Still, Naomi--though put off by Fredericks' macho demeanor--hopes for the best; meanwhile, she begins an affair with a sexy colleague and tends to her own ""So long, Daddy"" problem: she too was long ago deserted by a father--who has now resurfaced after 30 years. (Should she call him?) But soon it becomes clear that the kids, now out at Fredericks' East Hampton place, are in big trouble: Fredericks mocks Jason's lack of macho; he's interested in Maddie only as a potential model; he has two girlfriends on the premises (Jason sees them in lesbian action); the kids are puffing pot. And, despite a visit from Naomi and some informal group-therapy, things come to a melodramatic head. . . on Father's Day, of course: Maddie sniffs heroin (thinking it's cocaine); Jason, who's been getting firing-range lessons from Fredericks' homosexual assistant, starts waving a gun in rage; and Fredericks reveals the feeling-ful man behind the mask--in one of the phoniest sappy/happy endings on record. Paperback-author Gilmour (The Trade, several film novelizations) does a sometimes-convincing job with the kids' psychology. At its best her narration is urban-slick--with some OK Jewish-mother comedy. But the crucial father-character is a murky washout; the nonstop dialogue is an unappealing saccharine/vulgar mixture; and though the glossy-soap audience may find some tears and titillation here, other novels have treated similar father/child situations with far greater depth, Charm, and authenticity.