There's much that's attractive, warming and whole-grained in this growing-up confessional narrated by a young New York-based artist as she struggles to find herself in the world and on canvas. However, about halfway along, the pace slows to a crawl with a surfeit of talk about mainly painterly matters--issuing from the mouths of those in whom the author has apparently lost interest. Miranda and younger sister Portia have been more or less inured to hearing parents Desmond and Muriel ""damaging themselves"" in nightly rows. Desmond, alternately charming and quirkily depressed, was a successful radio scriptwriter and playwright but is now on the skids; Muriel, a self-dubbed ex-""soubrette,"" has longed for the exhilaration of an exalting exchange with theater audiences--and with the world. Desmond will come and go while Muriel, smothering her frustrations in obsessive house-scouring and in grooming her girls for taking on the world, disdains the talented Desmond's lack of nerve (his best work was always for other people); and Desmond, merely play-doctoring, is ""intrigued by what limits people."" Meanwhile, Miranda, who at nine was sketching portraits at a fireman's ball, will test her nerve, her limits. There'll be the inevitable tentative sexual adventures--until in high school she meets schoolmate and fellow artist Hugh, who has decorated a deserted railroad shed with Boschlike fantasies. Throughout schooling at Swarthmore and a Manhattan art school, Miranda and Hugh are lovers; yet Hugh declines into facile statement and a rotten life-style. Miranda searches, though, for a force within to shape her work--until a devastating critique sets her on the limitless but scary path to true feeling and artistic integrity, Miranda's early years--with parents and a varigated crowd of show-biz creators and precocious would-be's--are lively and cannily observed, but the attempt to convey the creative impetuses of a visual art (always a difficult and risky business) seems to dilute the characters and turns out to be rather a slog.