In a sequel to the popular Lizzie and Harold (1986), Lizzie again struggles with her tendency to overdefine a ""best friend."" This time, her now happily cooperative relationship with Harold is threatened when she becomes too possessive. The two start a ""Best Friends Club,"" but when Harold wants to include Douglas, Lizzie responds with unilateral proscriptions (""Best friends don't go to other people's houses to play""). Harold, sensibly, quits: too many rules. Lizzie sulks, but then an overture from Douglas allows her to come around gracefully. As before, the concerns here are childlike, the well-phrased dialogue believable, the illustrations attractive. Good for preschoolers or beginning readers.