What Is It? Spin about

First there were pop-up books. Then there were lift-the-flaps. Now comes a new variation on the theme: a ``spin-about'' book. What Is It? has only five double-spread pages, but they're all quite clever. A simple twist of the graphics (there are two connected shapes on each right-hand page, one of which is mobile) transforms an egg into a clamshell, a flying saucer into a pear, and so forth. This playful book gives children a hands-on look at the fascinating world of form and design. Ages 4-8. (Sept.)