Following fictional footsteps (by taxi)

It should have been a marriage made in heaven. Peter Hopkirk has an unparalleled knowledge of Kim country, the high hills to the north of India, where wise pundits and wily pathans have been playing out the "Great Game" of espionage for well over a hundred years. Indeed it was Kim, read when Hopkirk was "a highly impressionable, schoolboy of 13 - the same age as Kim himself", that, he tells us, did much to determine the course of his life.

In the 1950s he could get no closer to eastern approaches than the oriental bookshops off the Charing Cross Road. At last, in the 1960s, now a Times journalist, he managed to get posted east. After that he spent all the time he could spare from his career in mapping out the country and the culture in a series of books that are rightly renowned.

What could be more perfect than Hopkirk setting out to echo A J Symons' brilliant Quest for Corvo by applying similar literary detection techniques to Kim? To be blunt, an author who knew less and, for that very reason, told his readers more. Someone with the advantage of "beginner's mind", the intense excitement of first finding out that gives a book like Symons's, or Richard Holmes's Footsteps, such an engaging freshness of vision.

But Quest for Kim is full of good things. In an enthralling opening chapter, Hopkirk whets our appetite with quotes from such distinguished admirers as T S Eliot, Mark Twain and Wilfrid Thesiger, tackles the matter of Kipling's rotten modern image, and champions his work gamely.

He is also good on Lahore, where the story starts with Kim perched on the great gun Zam-Zammah outside the "Wonder House" of a museum. Its curator was based on Kipling's own father; and there is even a model for Kim: a by-blow of an Irish sergeant and a beautiful Tibetan girl who reputedly turned up with an amulet of documents around his neck in a Darjeeling bazaar in the 1870s.

But when Hopkirk gets out on the road and into his own familiar territory of the clandestine side of the British Survey of India that one gets a sense of being short-changed - in part, no doubt, because he feels that he is repeating himself. So the book's greatest weakness is what should have been its greatest strength: the journey across Northern India which is the backbone of Kim.

There are occasional triumphs - two Iranian spies hobbling across the Punjab with suitcases - but altogether too many physical cop-outs. "Unlike Kim and the lama, who slept out on the bare hillside, I spent the night in Mussoorie" and "leaving Kim and his caravan heading down to Saharunpore, for their route is far too vaguely described to try to follow, I went instead by road."

Proper literary detectives don't just quibble over real or not real; they live the books they love. Hopkirk needed more nights under the stars, more tumbles into rivers, more encounters with the thousand and one characters that make India the "bewitching and bewildering land" that he tells us it still is. To be fair, some of this lacuna is explained by the revelation that two-thirds of his way through writing the book, Hopkirk had the bad luck of losing "my entire set of notes for the remainder of the book."