Kin Platt's reputation as the author of "controversial" books for teen-agers is based on the not unreasonable assumption that anyone who manages to shock so many adults must be telling it like it is. In the past, Mr. Platt's candor has served him well, but Flames Going Out … is, just as the title suggests, a fizzle. When we first meet his heroine Tammy Darling (the name passes for irony) she is a mentally disturbed 16-year-old who has decided to resolve her sexual confusion through an affair with the drug-addict son of her Beverly Hills psychiatrist. Tammy's pursuit of this unlikely, and at times unwilling, love object is graphically portrayed, but this girl has so few resources for survival that one begins to feel like a voyeur for reading on to the inevitable conclusion. The setting of Tammy's odyssey, by the way, is decadent L.A., where her schoolmates...