Before Julius was born, Lilly was the best big sister in the world,"" but of course ""after Julius was born, it was a different story""--the usual tale of sibling displacement, anger, jealousy, and eventual acceptance. A familiar topic, but Henkes' delicately humorous narration--with its deft use of repetition reflecting Lilly's growing exasperation with the attention and special treatment Julius gets--makes this an unusually effective presentation. The expressively drawn characters--mice with very human clothing and domestic arrangements--are amusing and appealing.