Uegaki and Jorisch (previously paired for Suki’s Kimono
) bring poise and polish to a well-worn subject. At first Rosie’s perfect life seems even more perfect when little sister Buttercup arrives. Rosie sings and plays with her and teaches her to dance. In time, Rosie becomes disenchanted and gives Buttercup away—to her sitter, Oxford (in a typically fresh touch, Oxford is a middle-aged male). Predictably, she is soon sorry. A few basics are confusing: the well-dressed creatures do not belong to a recognizable species (possibly they are mice, but sans tails), and the passage of time is naggingly unclear—the story seems to unfold over the first months of Buttercup’s babyhood, yet she quickly becomes a surefooted toddler. Still, the book’s graceful treatment overcomes both uncertainties. Uegaki’s assured text assumes an intelligent reader: “One morning, Rosie woke up feeling peevish... a tiny idea that had been smoldering in her head burst into flame”; and offers offbeat images (“Rosie’s heart jumped like a poked frog”), which, like her well-chosen details, provoke giggles. Jorisch’s watercolor illustrations, uncluttered but dense with patterns, are crisp against generous fields of white space. Flowers and bumblebees loom big from the mouselike perspective; Rosie’s colorful toys, clothes and furniture bear cheerful witness to her pleasurable life. Ages 3-7. (Apr.)