A Box of Nothing — Peter Dickinson

For one young boy, a box full of nothing is a ticket to adventure While skipping school, James sees his mother on the street. He ducks inside an abandoned store, where an aged shopkeeper asks what he wants to buy. When James says nothing, the old man sells it to him: a heavy cardboard box stuffed full of top-quality nothing. James tries to explain this to his mother, but she doesn't believe him and throws the box over the fence and into the dump. He sneaks in to retrieve his new possession and finds himself trapped in another world. The dump is an eerie place populated by hyperintelligent rats, monstrous seagulls, and a very clever pile of garbage called the Burra. Once it was a thriving community, but something strange has happened, and the dump has become stuck in time. To get back home, James must help the Burra save the dump using all the nothing he can find.