This challenging book of optical illusions from Wick (A Drop of Water, 1997, etc.) will leave some readers gasping in awe, and others befuddled, as they ought to be by such visual trickery. Stunning photographs tease with false perceptions, shadowplays, and mirror tricks. Every photograph is a set piece (many of them sporting the same aesthetic sensibility of Wick and Jean Marzollo's I Spy books), and the opposite page asks readers various questions about what they're seeing. The very best pictures are patterned on the classic M.C. Escher drawings, paradoxes of impossible triangles, cubes, and other structures. Wick provides answers, ably explaining the perceptual twists, and adds an intelligent (and, for flummoxed readers, compassionate) closing: ""The variety of ways individuals experience optical illusions is in itself an interesting area of inquiry, but it's important to keep in mind that why such differences occur is not fully understood--even by experts--and that each reader should experience the book at his or her own pace."" A book to elicit appreciative murmurs at story hours, and return visits for closer looks.