Actually the twosome of the title starts out as a threesome: there's Rosie (short for Robert Rose), a good-natured klutz who's a whiz at the keyboards; Ronnie (""short for nothing"") Rachman, new in Uniondale, Long Island, and jittery over her first week at Ben Franklin Junior High; and Rosie's oldest friend, Evelyn Racanelli, a chubby mother hen type who immediately takes Ronnie under her ample wing. At first you expect a classic triangle to develop with Evelyn odd man out as Rosie and Ronnie start to make ""I like you as more than a friend"" noises. But no. Wisecracking Evelyn adjusts with good enough grace and so for half the book you're wondering what exactly is the purpose of this rather coy romance. Then suddenly from out of left field--or left lane--a car comes plowing into Ronnie's father, killing him instantly. In short order Ronnie's dithery artist mother turns into a walking zombie who refuses to adjust and who does her level best to see that Ronnie doesn't either--until finally a sympathetic gym teacher makes Mrs. Rachman see that both she and Ronnie need to be independent. Inoffensive, inconsequential, and basically the kind of book another more famous Judy does better.