Behavioral scientists with a nod toward Roots and the clean-living Carter clan forecast a return to the family, and certainly Patricia O'Brien's canny profiles of six couples holding on through the troubled tides of marriage support this perception. All have hit jolting mid-life crises without changing partners, though three out of six own up to playing superficial games of ""musical beds."" Nonetheless, journalist O'Brien, a self-described ""divorce statistic"" who won praise for insights on sexual freedom in Woman Alone (1973), suggests that Betty Friedan, women's libbers, and encounter groupies did not cry totally in vain. In each of these cases of ""shared history,"" the wives have worked at some time outside the home, ""which reflects one of the most important changes in marital life styles."" Out of the Sixties rebellion, an appreciation of the value of independence has emerged, O'Brien emphasizes, while the please-touch, open marriage proposition of the early Seventies has been examined and rejected as group groping in empty space. ""These couples are aware of outside perils and are trying to build up inside strengths. . . through bad times, good times, and forgettable times."" There's no pretense that this is a profound social study. The emotionally-loaded confessions of Jan and David Stein, Dorine and Bert Brodsky, Diana and Phil Morris, Anna and Jim Lowell, Liz and Peter Arthur, Laurie and Bob Kincaird, represent a limited segment of white, middle-class, child-rearing America. Still, through O'Brien's sensitive reportage, the contrasts between these uneasy Maytag marriages create a human documentary as riveting for receptive readers as Sheehy's Passages.