The southern Arabian desert, a quarter million square miles of sand (650,000 square kilometers), is now a place of oil wells and Land Rovers, but before the 1950s it was still known as the Empty Quarter, a place you entered only on camel and only as an Arab. Only a few white men had ever seen it, much less crossed it. From 1945 to 1950, the British Thesiger crossed it twice, living with the Bedouin, sharing their hard lives. His book is the classic of desert exploration, a door opening on a vanished feudal world. It is a book of touches, little things-why the Bedouin will never predict the weather ("since to do so would be to claim knowledge that belongs to God"), how they know when the rabbit is in its hole and can be caught. It is written with great respect for these people and with an understanding that acknowledges its limits. With humility, that is, which is appropriate. Fail the humility test, and the desert will surely kill you.