Sir John Mandeville, a medieval English knight, was either one of history"s greatest explorers or one of its greatest liars, depending on how one reads the pages of his Travels. Christopher Columbus took his words as a veritable guidebook, using it, Giles Milton writes, to convince the Spanish crown to fund his American voyages. The Victorians were not so kind, dismissing the wanderer--who, after all, wrote that in the Indian Ocean "there is a race of great stature, like giants ... they have one eye only, in the middle of their foreheads"--as an uncritical fabulist at best, a charlatan at worst. Giles Milton, a student of exploration history, gives us reasons aplenty to question Mandeville"s accuracy at points, but he is inclined to think that the knight actually did see at least some of the things he reported in his enormously influential book. Tracing Mandeville"s trail to the Middle East and beyond, he considers the historical realities that underlie Mandeville"s tales, from the gems that lie strewn among the reeds of Indonesia (which Milton guesses might be crystal-like secretions from bamboo plants) to the fabulous Christian kingdom of Prester John somewhere far out on the plains of Mongolia (where, Milton reminds us, Nestorian Christians were once common). His conclusion, well argued in the course of this witty and delightful book, is that although Mandeville is not always taken literally, he really did go crusading off in distant lands, and he certainly deserves to be rediscovered today, not least for what his work tells us about the medieval mind. Readers new to Mandeville will find this a spirited introduction, and those already fond of The Travels will enjoy following Milton"s parallel voyages. --Gregory McNamee