A Boy and His Bot — Daniel H. Wilson

When Code falls down a hole while following a mysterious robotic insect, he lands in a world that defies all imagination. Everything in Mekhos is made from metal and circuitry, including the citizens, who just happen to be robots. To find his way home, Code must venture to the Beam Stalk where a powerful artifact is being protected by an evil ruler. Can Code save the robots from impending doom and still get himself back to Earth in time for the school bus?