All of Elmsville is excited to hear that Mr. Duncan and his family are off to N.Y.C. to visit the great Serena Katz--but is she who they think she is? The postmistress remembers her as ""the Katz Meow,"" the West Side's best pool-player; a neighbor as a show-stopping magician; another as the creator of fabulous wedding cakes; and yet another as ""Krazy Katz,"" motorcycle racer. Mr. Duncan knows only that she runs a hardware store and buys his paint. Alley, whose watercolors are, as usual, lively and well-crafted, does a wonderful job of building anticipation, depicting everyone's memories but showing only a glimpse of Serena Katz's hand or foot in each scene. When at last the Duncans reach her door, they find a pleasant little old lady in sneakers who briskly sends them on a whirlwind tour of the city. Are the stories about her true? Oh, yes, and more besides. Has she left all that behind? Not likely: the spirit of adventure is ageless. A treat for readers who find Miss Rumphius a bit too genteel.