Mark Cooper's father, wintertime caretaker of posh East Hampton estates, is a cagey, ingratiating alcoholic; his mother is a TV-serial addict and garage-sale freak; and there's also insanity and suicide in the family. So it's not surprising to find 17-year-old Mark a systematic, conscientious Straight Arrow: in the trendy teen vernacular in which he narrates (which, mercifully, eases up as the story progresses), he's a ""latent insaner""--also an ""undiscovered genius,"" a ""future mile-record holder, and super lover, and a whole bunch of other things."" One of the book's problems is that the labels don't coalesce into a personality with any weight; and that's a particular handicap when Mark meets rich, gorgeous runaway Para, a chronic liar and mistruster and, as she's labeled, in almost every way Mark's antithesis. She's hiding out in her stepfather's summer house; the two click; and Mark is torn between attraction and responsibility: not only should he tell her stepfather, but the Coopers can't afford to lose another client. (He tells--promising, however, to see that Para gets home.) The Mark/Para affair (cum sex) has to be taken on faith most of the way; but the problem of Tom Cooper's drinking is appallingly immediate--climaxing in a ghastly scene of DTs, Tom's shunting from hospital to hospital, and his assignment to a dry-out program which he's skipped out on before. In the course of this imbroglio, Para proves herself to be a steadfast, sensible helpmate: violence and hostility don't throw her. And eventually--via some textbookish psychology--she induces Mark to express his hostility toward the man-his-father's-become. That, in turn, triggers a less-than-credible about-face in Tom: he'll stick out the program, even join AA. Finally we see Mark sufficiently relieved of his anxieties to plop a discarded top hat on his head and act ""crazy."" It's all rather too neat and obvious to make a lasting impression, but it does draw the reader in and along--and there's more than a little truth in what it has to say.