Adler and Miller previously tackled Circles (2016) and Triangles (2014); now they add quadrilaterals.
The duo start off slowly (though not as basically as in the previous two books) and build the learning as the pages turn. Polygons with four straight sides are quadrilaterals. If their sides are of equal length and their angles all measure 90 degrees, they are squares. Using a ruler and a “right-angle tester” (a corner cut off an envelope), readers can test shapes. An analog clock is used to introduce angles and their measures, and as in Triangles, Adler encourages readers to snip the corners off quadrilaterals they have drawn and put their vertices together, proving that the angles always sum 360 degrees. The rest of the book defines other types of quadrilaterals: three types of trapezoids, a rectangle, a rhombus, a kite, and a parallelogram. The use of an empty cereal box to help children visualize shapes is rather confusing, and the digital illustrations are a little busier here than in the previous titles, the measures and marked angles sometimes visually overwhelming. Unlike Circles, the learning is not nearly as deep: This is more a glorified shape book that looks only at shapes with four sides and defines vocabulary, so the audience and format are a mismatch.
This has its place in the series but is not as strong as the previous two. (glossary) (Informational picture book. 6-10)