I don't mind women's lib--only women's lip."" That's how eight-year-old Tullius Cicero Sharp IV, known as Tad, explains his problems with four bossy older sisters. And when the girls plan Ma's birthday dinner without consulting him, Tad decides to go downtown alone to buy his own present and then finds himself without bus fare for the trip home. Tad's walk home after dark is truly scary--a lonely park, the lighted windows of strange houses, a burntout mansion, even a neighbor's bull terrier all feed his active imagination. Otherwise this is one of those narrowly focused gestures of independence that relies on the reader's own feelings about. big sisters to provide the emotional stuffing.