A lackluster entry in a generally likable series. Foreboding sets in as soon as we learn that neat, systematic, smart seventh-grader Karen has elected, as a special project, to do a Time Efficiency Study of her ""easygoing household""--especially to make-over sloppy, lackadaisical stepsister Vicki, 16. But before that inadvisable project can get underway, we have to learn who's who in the ever-growing, increasingly complex family that began, a year or so back, with adopted Korean orphan Karen and her unmarried veterinarian Mom. Then: Mom adopted another Korean orphan, six-year-old Meghan; on the way home from the airport they had a flat, and Mom met Dad, a local science prof; now they're married and living (temporarily) in his too-crowded house with his three kids and his mother, who does most of the housekeeping--particularly now that Mom (and Dad) will very soon be having a baby. Karen's efforts to reform one-and-all are not very ingenious or even very intelligent: mainly, she puts up lots of THINK-type signs. Vicki is understandably hostile. Dad eventually wises Karen up: having ""self-confident"" Karen around isn't easy for Vicki; if Karen changes, maybe Vicki will too. But the big changes, for everyone, come with Grandma's heart attack: Vicki repents of being curt to Grandma (and Karen), and confesses her insecurities; everybody pitches in, systematically, to take over Grandma's chores. And--the book's brightest moment--Karen decides against entering her Time Efficiency Study report for a state prize: the contents would have humiliated Vicki. OK for regulars, but without nearly the snap of its forerunners.