After the author of her favorite series of books, ""Sandy the Super Dog,"" moves in next door, Rosie discovers how imagination (both hers and the author's) can be related to reality. Disappointingly, Dawn O'Day--though courteous--seems to be determinedly reclusive; she firmly rejects Rosie's persistent advances, refusing to give an interview for Rosie's hastily concocted newspaper or to hire her to do windows. Then a thunderstorm knocks out the power, bringing Dawn to Rosie's doorstep for an impromptu neighborhood gathering; good feeling is cemented when Rosie and her friends recover the real Sandy, a placid golden retriever, after he strays from home. Rodowsky, the accomplished author of (most recently) Sydney, Herself (1989), enriches this well-worn plot with her unusually well-drawn characters (the lively interaction between Rosie and her little sister, and between Rosie and her formerly despised new friend, are especially engaging), and with the girls' delightful curiosity about words like ""nefarious"" and ""splendiferous."" Best is Rosie's gradual realization that it's ordinary-seeming Dawn's imagination, rather than the phlegmatic Sandy's real activities, that is the source of Sandy's lively fictional adventures. An excellent choice for readers graduating from the Cleary books.