Great travel writing is about sharing with readers a state of mind born of experience and filled with mystery and mistake. Colin Thubron, who ranks among the gods of travel literature, set out at the age of 64 to trace the 'fretwork' of paths that make up the 11,300km Silk Road from Xian in China to what is now Antakya in Turkey. The journey took eight months, not counting a halt owing to warfare in northern Afghanistan. However, Shadow of the Silk Road, his ninth travel book, represents decades of travel, the more remarkable because Thubron is revisiting places his memory 'had reduced ... to a few lanternslides'. He last saw China before it became a market economy and the 'autumnal mud' of Xian is now shopping malls, brand names and 'couples walking hand in hand, even kissing - a Maoist outrage'. The Afghan city of Herat of 30 years earlier has all but vanished in diesel fumes, but 'beneath this clamour an old suavity and grace survived'. Borders may change, but Central Asia remains a chaos of contradictions. Shadow of the Silk Road is about how life along it has changed in a millennium, and also in a mere lifetime.