When is a pop-up book not a pop-up book? When it's also a play space for youngsters 5 to 8, featuring paper models with moving parts and accessories. Paper engineer Robert Crowther presents this celebration of fascinating construction machines — a dump truck, bulldozer, tractor, forklift, and tower crane — each at the center of its own pop-up tableau. The book describes what the machine can do and provides facts about its size, weight, and capacity, while in storage pouches are such accessories as trailers, tractor blades, cargo pallets, and construction materials, which can be unfolded and used with the heavy equipment.