The book has two settings. The story begins in the real world, in a large modem city much like New York or Chicago, where Milo lives on the eighth floor of an apartment building. He walks home from school along busy streets, past a vast array of buildings and shops, but nothing ever interests him enough to cause him to look up from the pavement. Although his room at home is filled with toys and games, he does not enjoy playing with any of them. One day he arrives home from school and discovers a huge package sitting in the center of his room. Inside is a turnpike tollbooth, just the right size to go with his small electric automobile. Having nothing better to do, he assembles the tollbooth, gets into his car, and drives up to it.

Suddenly, without any warning, Milo finds himself driving down a...