One might have thought that there was little need for another book on the Great Wall, especially after Arthur Waldron's masterly study, but Lovell demonstrates that the subject is far from exhausted. She brings together facts and figures to show what an awesome engineering feat the construction of the wall was. It included enough bricks to build a wall five meters high and one meter thick to encircle the globe; the sections that still stand would be sufficient to link New York and Los Angeles. Yet Lovell's interests lie more in how the wall shaped Chinese political and strategic thinking. The wall served contradictory purposes for China's rulers: it was there to keep the barbarians out but also to awe outsiders, to protect the Chinese people from outside forces but also to prevent exposure to the outside world.