Dubus, master of the Catholic-family/divorce short story, stretches his material a bit thin in this novella--with six members of a north--Massachusetts family reacting to the latest in a series of marital crises. ""It's divorce that did it,"" says Greg Stowe, 47, who has decided to marry young Brenda, ex-wife of Greg's son Larry, 25. Understandably, this announcement disturbs Greg's twelve-year-old son Richie, who's only just gotten used to his parents' recent divorce: Richie, living in the old family house with his protective father, feels responsible for everything, determined to do right and preserve his plans for priesthood--despite puberty's stirrings in the person of 13-year-old Melissa. (""From Christ he had to receive the strength or goodness or charity or whatever it was to give his father and Brenda more than forgiveness and acceptance. . . . And he had to be with Larry outside of the house, as he saw his mother now. Saint Paul had written that all the works were nothing without love. He had to love them all, and he could do that only with Christ, and to receive Christ he could not love Melissa."") And other family responses emerge in less satisfying close-ups: Larry recalls his brief marriage to Brenda, which revolved around her promiscuity and his voyeurism; Brenda ponders her husband-to-be's bar cronies, their boyish ways; Greg visits daughter Carol, 26, who is warm and supportive; and Larry takes his anger to divorced mom Joan, now a contented waitress who assures him that his rage will fade. (""We don't have to have great lives, we just have to understand and survive the ones we've got."") More sentimental and diffuse than the top-drawer Dubus stories, and far too slight to merit a solo book-form appearance--but occasionally touching in its broken-family recognitions.