Too short a biography of a great biographer

<i>Boswell's Presumptuous Task </i>by Adam Sisman (Hamish Hamilton, &pound;17.99)

Life is short and biographies are long. Each of us has time for just one nifty, reliable account of even so magisterial a figure as, say, Nelson, but each also has enthusiasms whose progress from cradle to grave we simply have to read in every new version. Whatever the paucity of new information, wallet is emptied and shelf filled. This season, for example, there are evidently some readers who need another thousand-odd pages on Wordsworth, or a retread of The Beatles' history.

Life is short and biographies are long. Each of us has time for just one nifty, reliable account of even so magisterial a figure as, say, Nelson, but each also has enthusiasms whose progress from cradle to grave we simply have to read in every new version. Whatever the paucity of new information, wallet is emptied and shelf filled. This season, for example, there are evidently some readers who need another thousand-odd pages on Wordsworth, or a retread of The Beatles' history.

Some of us simply cannot resist another account of James Boswell. This one, by Adam Sisman, follows last year's heftier volume by Peter Martin in overlooking a 1925 essay by Lytton Strachey. He observed that "it would be difficult to find a more shattering refutation of the lessons of cheap morality than the life of James Boswell. One of the most extraordinary successes in the history of civilisation [his Life of Samuel Johnson in 1791] was achieved by an idler, a lecher, a drunkard, and a snob. Nor was this success of that explosive kind which is frequent enough with youthful genius... it was the supreme expression of an entire life... self-indulgence is common, and Boswells are rare. The precise character of the rarity we are now able, for the first time, to estimate with something like completeness."

Rash words. Just as some of Boswell's letters had surfaced as wrapping paper, so the journals and other papers duly emerged in croquet-boxes in Ireland and Scotland, where one happier consequence of war was the need to create a grain store in a farm building. One pictures that scene, heart pounding: the workmen could so easily have hurled the manuscript of the Life on top of the pile of timber under which it had languished.

Sisman concentrates on the creation of the Life. He shows a Boswell who is all too human, yet appears almost superhuman. As Strachey put it, "the same force which produced the Life of Johnson plunged its author into ruin and desperation. If Boswell had been capable of retiring to the country and economising, we should never have heard of him." Sisman's serviceable prose is never as pithy as that, but he traces reliably the path by which Boswell's surname has come to denote a trade - that of a faithful chronicler, a sedentary gofer, even a toady.

The truth, as Sisman rightly emphasises, is more subtle. For Johnson and Boswell, seer and supplicant, not only shared many traits - above all, paralysing hypochondria - but were in each other's company far less than the popular imagination has inferred from Boswell's adroit manipulation of his material.

By a seemingly egotistical method, Boswell's work of art anticipates the Romantic era. It took a long time for the strengths of the Life to recover from a bullying essay by Macaulay - whose subject was in fact an edition by Croker. With none of Boswell's sense of pace and drama, Croker bunged in all that had emerged since the biographer's death. That situation risks being compounded by all the papers discovered later - quests thrillingly told in David Buchanan's The Treasure of Auchinleck.

Such is progress on the current Yale edition of Boswell that those as-yet unborn might not see it completed. But Sisman draws heavily upon Marshall Waingrow's elegant, 750-page edition of letters about the making of the Life (1969). Again, one aches at Boswell's task. It was one at odds with the spirit of the age, and beset by urges which, debilitating and humiliating, did not lessen grief over his wife's death.

The wonder is that anybody, however disciplined, could have produced so large a book in seven years. After all, Adam Sisman has been occupied for a similar time with this far shorter one. While making vivid the many grey areas of a man whom moralists too often see in black and white, Sisman leaves the way open for another book. Brisk as his is, it is for those familiar with Boswell. Those who are not need something else, a book akin to Christopher Hibbert's "personal history" of Dr Johnson - that worthy pendant to the Life that has made many inhabitants of desert islands oblivious to a ship on the horizon.