"It came upon me suddenly," Osborne reports, "like a mental disorder unknown to psychiatry: the desire to stop everything in normal life, to uproot, leave." And so he does, taking off on a six-month journey from Dubai to India, Bangkok, Bali and Papua New Guinea on the "Asian Highway." Osborne is not just interested in travel, but also in the reasons why we travel, layering his own entertaining adventures with ruminations on Shangri-La, The Grand Tour, the exotic and primitive.  (SEA50, $14.00)