BOOK REVIEW / Cracked domes on the silk route: 'The Lost Heart of Asia' - Colin Thubron: Heinemann, 16.99 pounds: Colin Thubron's new book explores the timeless barges and palaces of Central Asia. William Dalrymple follows him

NO ONE today remembers the legendary greatness of the Seljuk Sultans of Merv. The ruins of their once magnificent capital lie now amid the camel-coloured wastes of Turkmenistan: a scatter of mud walls, a few ambiguous foundations, the cracked dome of a mud-brick Muslim tomb. This ghost capital lies forgotten now on the outer edge of a polluted and provincial Soviet town: on one side a forest of smokestacks belches fumes into the desert, on the other, a spread of barren collective farms extends towards the encroaching dunes.

Yet in the 10th century AD, while Europe lay paralysed under a deluge of Viking raids, Merv was the second city of Islam: a flourishing Silk Route capital, fabulously rich on the profits of the China trade and the tribute of an Empire which extended southwards from Afghanistan to Egypt and the gates of Byzantium. Along with its great sister cities - Tashkent, Bukhara and Samarkand - Merv developed a rich culture, fostered in a series of learned universities, and blossoming in such geniuses as al-Biruni (who first computed the radius of the earth), the lyric poet Rudaki, and the great Ibn Sina, known in the West as Avicenna, who wrote 242 books of stupefying variety and whose Canons of Medicine became a textbook in the hospitals of Christian Europe for over 500 years.

This fabulous, almost mythical world was shattered in a single year when the horde of Genghis Khan swept through Turkestan, destroying everything that stood in its wake. It could have recovered - but then Europe discovered the sea route to the East and the Silk Route caravans grew infrequent, finally drying up in the 17th century. 200 years later, the Czar's armies were able to conquer the whole region - an area the size of Western Europe - with just 40 casualties.

In 1992 Colin Thubron travelled through this region as it was passing through another turning point in its history. The lightning retreat of the Soviet Union had left Central Asia beached and disorientated on the desert sands. Five new states had suddenly emerged stillborn into the world: Kazakhstan, Turkmenistan, Tajikistan, Kirghizistan and Uzbekistan. Their boundaries and names had been created by Stalin on an imperial whim; they bore as little relationship to the underlying tribal realities as those of post-colonial Africa. Each possessed a confused hybrid culture, the result of the strange coupling of high Soviet Marxism with the mystical Islamic civilisation of Timurid Central Asia. Suddenly no-one knew what to believe. The old identities had collapsed, the old certainties were dissolving, and the old order had turned, in freedom, to chaos.

It was the ideal moment for a travel writer. Thubron found a people who were openly asking fundamental questions about themselves: Who were they? What kind of government did they want? Should they follow Turkey's secular lead and form a new pan-Turkish block? Should they ally with the mullahs of Tehran and look to Islam for their answers? Should they revert to the certainties of Marxist- Leninism? Characteristically, Thubron refuses to give any answers. He has always been the most detached of modern English travel writers, a cool Anglo-Saxon observer who travels alone, has no ties and no loyalties, and who never judges. In this book, as in its predecessor, he simply presents a series of lives pinned dispassionately to paper like the butterflies of a Victorian collector.

He certainly finds rich material in the remote towns and farms that he visits: the stranded Russian professionals who decided to 'stay on' after the collapse of the Soviet Empire and who now, like the Calcutta boxwallahs of the Fifties, feel lost and confused amid the heady nationalism of the newly-liberated republics; the Bukhara Jews who know no Hebrew and whose esoteric practices are regarded with horror by Orthodox rabbis; the shadowy cohorts of Naqshbandi Sufis who outwitted the KGB's attempts to infiltrate their brotherhood, and who are only now beginning to emerge into the daylight. No less riveting are some of the obscure stories from the Central Asian past that Thubron dredges up: the wicked Khan of Khiva who awarded his warriors with robes of different grades of silk - depending on the number of enemy heads they brought to him in a sack. Odder still is the ruined farm built by a curious community of pacifist Mennonite settlers: escaping compulsory military service in Prussia they loaded their possessions on a barge and somehow ended up settling near the palace of the Khivan Khan, arguably the most brutal court on earth.

As with all Colin Thubron's books, the principal pleasure of The Lost Heart of Asia is his exquisite prose: Thubron writes with an originality and vividness that few contemporary authors can match. Indeed, at times his prose is perhaps too polished: Thubron has a relentless urge to poeticise the human condition, to pick over and interpret every last gesture and conversational nuance. The superfluity of fine phrase-making gives the writing at the beginning of the book a curiously opaque quality, clogging the narrative and making for a sluggish start, but once he gets into his swing this passes and the book begins to fill with the sad and animated fragments of other people's lives that Thubron is so good at capturing.

I don't think this will be remembered as Thubron's best book: it somehow lacks the cast-iron conviction and authenticity of his great work on China, Behind the Wall. But in a genre that has been drowned over the last decade by a deluge of dull and mediocre minor travelogues, it is good to know that there is still a master at work whose second division books are still in a different league from those of almost all of his rivals.

(Photograph omitted)