With the intriguing idea of exploring what lies below the surface of the Earth as its broad theme, this fascinating book cleverly dices up the subject into small, more manageable pieces ready to be devoured by young readers, particularly boys. The basics are covered in detail, such as the physical properties of the Earth's crust (including its unusual features such as volcanoes and caves), as well as animals with underground habitats. There is a treasure trove of information on the uses humans have made of the underground --- from bunkers used during wartime, to burial sites, to the Paris Métro --- as well as possibilities for the future, even on Mars! What makes this book truly unique, however, are the less expected subjects it covers --- fully examining, for example, the subterranean city of Cappadocia, where early Christians hid from Roman soldiers; King Tut's tomb and its alleged curse; and the underground dungeons used for torture in medieval castles.