THERE ARE BIG books on large subjects, and there are little books on small subjects. And then there are the eccentric hybrids: books about people who wrote big books on large subjects.

This genre has been burnished to perfection by Simon Winchester, an author drawn to once famous but now obscure men who dedicated their lives to one great idea. Such is the focus of Bomb, Book and Compass.

The central character is Joseph Needham (right), a Cambridge don whose career spanned most of the last half of the 20th century. The great book is Needham's multi-volume Science and Civilization in China, a work that sought to chronicle the entire corpus of Chinese science from antiquity to the present and to explain why China once led the world in innovation yet did not become the birthplace of modern science. Needham came to his subject unexpectedly: he had started his academic career as a promising young biochemist at Gonville and Caius College. A young eccentric, drawn to nudism and openly not monogamous with his quiet scientist spouse, he met and fell in love with a Chinese student who had made the long journey from Shanghai for the sole purpose of meeting him. Their bedchamber led to his study of Chinese, and that in turn led to his appointment after the outbreak of war as a cultural ambassador to China in 1943.

His official appointment was to head the Sino-British Co-operation Office, a rather extraordinary wartime role designed to shore up the morale of Nationalist China by aiding its scientists to continue their work and make sure that they had supplies. Once in Chongqing, smack in the centre of the country, Needham set off by truck and convoy throughout the country, save of course for the coastal areas occupied by the Japanese. Though purportedly a liaison, he took the opportunity to explore the country with an eye to investigating the scientific legacy that he believed was understood neither by Western scholars nor by the Chinese themselves. The capstone of these efforts was an arduous trek to the Silk Road and the caves of Dunhuang, where a trove of scrolls had been found at the turn of the century, one of which, the Diamond Sutra, had been printed on a printing press centuries before such a device had been invented in Europe.

The journey to Dunhuang is the centrepiece of Winchester's tale, and it is engagingly told. But it is also something of a trifle, a synecdoche that conveys a China past and the odyssey of one man to honour its legacy. Like all of Winchester's prose, these pages flow easily, and create a vivid sense of the vast barren beauty of western China in an era when travel was still measured in weeks rather than hours. That said, here, as elsewhere in the book, it is hard not to stop occasionally and wonder if the story is quite as portentous as billed.

When Needham returned to Cambridge, he promptly petitioned the college masters to relieve him from his science-teaching duties to allow him to focus on what would become the work of his lifetime, which he spent the next 50 years composing. As the volumes trickled out, through riots, revolutions and upheavals, Needham's reputation sank after he was duped by the Communist Government of China into validating false claims that the US had used chemical weapons during the Korean War, and for the next 20-odd years he was not permitted to visit the US and faced years of hostility from his colleagues.

But as the first sections of his magisterial work appeared, the reviews were glowing. He succeeded in demonstrating to a sceptical Western world that China was “for much of its great age a highly sophisticated civilisation ... and quite possibly the fount of just about everything ... important that was known to the outside world”. That included not just bombs, books and compasses, but everything from air-conditioning to water mills, clocks to stirrups and the toothbrush.

Winchester does have a tendency to hyperbole: “Like nowhere else on earth, and like no other time in history.” Even when the sentiments are merited, it can feel as if the author doth protest too much.

There is also a nagging tree-falls-in-the-forest question, namely, if Needham's fame and work has faded in such a short time since his death in 1994, how true can it be that his work fundamentally altered our collective understanding of China's central role in human history.

Yes, Needham was always an academic celebrity, but he didn't have the crossover fame of others such as Toynbee or Hobsbawn, nor were his books - however lauded - widely read. His contribution may have been as fundamental as Winchester avers, but in the end, the conviction that Needham fundamentally altered Western understanding of China remains just that.

Instead we are left in the end with one man's graceful, diverting account of another man's passion, and that has its own worth.

Bomb, Book and Compass: Joseph Needham and the Great Secrets of China by Simon Winchester
Viking, £20; 336pp Buy the book

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