More child-friendly than last year's 600 Black Spots, the new addition to the series that began with One Red Dot is just as much an overture to exploring art. A yellow square hides in plain sight in or within the paper engineering on each spread; sometimes, the creation of the yellow square is entirely up to the reader. On the first spread, for example, that square exists only when the reader peers through a die-cut while holding the book at the correct angle—in other words, perspective is everything. Captions are variously enigmatic (“The fog of art/ and a yellow square,” for an elaborate windows–like construction topped in vellum) or childlike (“The cow jumped over the moon/ and a yellow square,” for an abstract paper sculpture). As before, Carter confines himself to primary colors, black and white; even with this palette, he alludes to a number of artists, among them Agam, whose name he spells out in a tribute piece; Christo, in a trio of wrapped structures; Miro; and Calder, via a trapeze with rotating flaps that stand in for performers. Not all the spreads are equally impressive, but the best are dazzlers. Ages 3–up. (Sept.)