COME BACK, JACK!

Jack can't read yet; still, he loves books so much that he slips right inside one, leading his older sister, who follows, a merry chase as he becomes one ``Jack'' after another. From the bottom of the hill where she's spilled her pail, Jill sends the sister on to the house that Jack built, where he's jumping over a candlestick; in the end, the two escape from a giant down a beanstalk and back out of the book. The adventures are whisked through rather than developed, and the conclusion (``perhaps books aren't boring after all,'' muses the sister) falls a little flat, but tots will enjoy identifying favorite characters, especially in the lighthearted illustrations. The relevant rhymes are included on the endpapers. (Picture book. 3-7)