There are certain invariables in the chick-lit universe: a twentysomething heroine working her way up the career ladder; a wisecracking sibling to provide comic relief; and, of course, an unattainable guy for said heroine to pine over. French's debut novel mixes in the doozy of a middle-aged mother (harboring a shameful secret) dropping in on her 23-year-old daughter Claire for an extended stay. The execution of the formula is enjoyable enough, and Claire's musings on her quarter-life angst are unexpectedly poignant: ''My friends...had shallow savings accounts and limited imaginations, and I was always left wishing I was with someone more interesting. Someone a little less like... me.'' ''sMothering'' may not be as fun or as well plotted as ''Bridget Jones,'' but the emotions ring true.