The entries in the Box Pops series do not at first seem to be books at all. Packaged in colorful, chunky little boxes, they look more like cardboard toys. But lift the lid and the pages come out, accordion-style. Each tiny spread features a single subject-a toy, animal or article of clothing, depending on the book-depicted with uncomplicated graphic flair. The Pets box might be a travel carrier for animals; in it a pop-up dog wags his tail and a parrot spreads its wings. Clothes is like a hamper, holding, among other laundry items, socks hidden behind pull-up pants legs and a belt that can be unbuckled. Toys houses a fire truck with a raised ladder, a robot with movable parts, a dollhouse with a lift-the-flap shuttered window. The bare-minimum text simply labels each item, leaving it to readers to make up their own stories or games. Ages 3-5. Apr.