ONCE upon a time, a young man went for a walk. It was December 1933, and an 18-year-old Englishman named Patrick Leigh Fermor put on a pair of hobnail boots and a secondhand greatcoat, gathered up his rucksack and left London on a ship bound for Rotterdam, where he planned to travel 1,400 miles to Istanbul -- on foot. He had virtually no money; at best, he'd arrive in, say, Munich to find his mother had sent him $:5. But what he did have was an outgoing nature, a sense of adventure, an affinity for languages and a broad network of friends of friends. ''If I lived on bread and cheese and apples,'' he later wrote, ''jogging along on fifty pounds a year like Lord Durham with a few noughts knocked off, there would even be some cash left over for papers and pencils and an occasional mug of beer. A new life! Freedom! Something to write about!'' [ABSTRACT FROM PUBLISHER]