A first novel of unusual buoyancy, snap and high spirits, about the straining and then liberating loosening (but never severing) of family ties on the way to adult life and love. Nothing ponderous or pretentious here, however--just an invigorating spin around a young woman's wrestle with the vagaries of family and romantic love, brought off with energy and class. Soap-opera actress Una Cavan, 29, whose TV character in Beyond the Bridge is temporarily lost in the north woods, is able to take a late summer breather in Newport, R.I., where younger asters Lily and Margo, grad students at Brown, are messing around with boats--and sailors. After a lengthy separation, they're close again in a tri-sisterly knot, tossing off coded family banter as always. Lily and Margo are particularly solicitous of Una--because she's just seen and talked to Dad. And Dad has died a month before. But Una claims the handsome charm-anything-off-anything James Cavan appeared to her in ""true corporeal splendor,"" seated on the john, reading the Daily News. Always the patriarch, in spite of his earthly bouts of alcoholic ""Black Ass"" bar-hopping, James lays on advice--things like telling Mother, who's in a fog of watercolor painting, to prop up the ceiling of her Connecticut house, and ordering Una to lay off ""pukes"" like lover Boom-Boom. The sisters at one point take their traditional ""sea cruise""--a hellfire drive down the beach with beer and butt smoke, ""six breasts abreast""--but hanging over them is the thought: ""It's time to get married."" Lily does, to a Dutch surgeon, stern and blond Henk. He's rich and thick, and Una hates him for making Lily all little-wifey and clinging. Meanwhile, Una is back at work, famous and lonely. There's an interlude with jaunty Joe Finnigan (another patriarch in the making?); a standoff with Henk and Lily; a thrilling movie offer; Europe; and a visit to Margo and nice Matt in his inn on R.I.'s south shore. It's there, in a stunning turret room, that Una and oceanographer Sam will first make love; and where Dad will appear, on a cloud, with last-minute thoughts. There'll be an off-and-on affair with Sam, a wedding, and a last sea cruise before the sisters and the memory of a father let go--in love. Bright, funny and warming, a promising talent much in evidence.