Why Richard Stern's Other Men's Daughters gets better in its final chapters

Credit where it's due: The last third (haven't quite finished reading it yet - there's a short part 4, something like a coda, still to come) of Richard Stern's Other Men's Daughters (1973) is the best part of the novel. Why? I think because in this section he more or less forgets about protagonist Robert Merriwether's love interest, Cynthia (who one imagines will inevitably toss Merriwether aside eventually), a beautiful and brilliant undergrad who falls for/seduces/bewitches the Harvard prof twice her age, and focuses on Merriwether and his family: the icy hostility of his wife, Sarah, and his guilt about breaking up their marriage and his pathetic attempts to rationalize and to be kind; the difficulty of explaining their pending divorce - and the reasons for it - to children, colleagues, neighbors; the legal mechanics of the divorce and the attendant troubles, such as selling the family house and finding new lodgings for all. Stern does a fine job with a few of the scenes, especially the painfully awkward last xmas the Merriwethers will celebrate together. He's not a great stylist, a la his contemporaries Roth and Updike, who have similarly examined marital despair and academic rites, but he has a great eye of what Wolfe called "status details," the many objects and acquisitions and decorations that mark a space and from which we, like anthropologists, can determine gender, race, class. Stern builds toward the climactic scene in which the parents tell the two youngest children - they seem to be in high school or maybe middle school - of the impending divorces. Improbably, they wait till the last possible moment, virtually on the eve of moving out of the house - but it's still a sorrowful moment, and we even feel some pity for the dad, even though he brought all this about through his own infidelity and ego. This novel, as one might deduce from the title, is entirely from the male point of view, but in fairness to Stern we feel more sorrow and pity for his wife (and children) than for the male protagonist; I almost wish that he's written a companion piece - like the Mr. and Mrs. Bridge novels - covering the same period of time and the same ground in close 3rd person from Sarah's POV.