Yes, I know you've already got a copy of the Life; so have I, somewhere: a nice old two-volume Everyman edition, portable, with a serviceable index - and rarely consulted. So when I saw this, I thought it might be unnecessary: expensive and unwieldy, not really Penguin's kind of thing at all.

You can't read it through in one go, of course, that would drive you mad. (Its composition very nearly drove Boswell mad; and you also have to feel for his poor printer, who must have suffered as much as Proust's.) This edition is more than 1,000 pages long before you even get to the appendices, notes and indexes - four of them, along with nigh on 1,300 notes. (These, incidentally, are very useful, though you don't get the feeling that they're compulsory.) But as the book became part of the furniture, it became less and less intimidating. Once you realise that it's for dipping into, it becomes much less imposing: an 18th century treasure trove rather than a monumental classic that demands dry and serious attention.

It is, of course, quite barmy. That is why it is such fun. Just as Burton's Anatomy of Melancholy was one of Johnson's favourite books - insanely digressive and inclusive - so this has a similar quality. Everything that can go in, goes in. (It is the kind of work that, like the Anatomy, would have got Johnson out of bed two hours earlier than usual. That is, about 10am.) Fretting that Johnson did not write a full account of his trip to France in 1775, Boswell reproduces, in its entirety, Johnson's notebook covering the dates from 10 October to 4 November. "My readers, I am confident, will peruse it with pleasure" - and we do, even though we may find the information we gather of debatable utility. And yet, why not learn that Julien le Roy, the King's watchmaker, is "a decent man"? And our literary heritage is all the richer for the mystery of what Johnson did with his orange peels. (Johnson: "I have a great love for them." Boswell: "And pray, Sir, what do you do with them? You scrape them, it seems, very neatly, and what next?" Johnson: "I let them dry, Sir." Boswell: "And what next?" Johnson: "Nay, Sir, you shall know their fate no further.")

This is one of the great virtues of Boswell's work: it shows us how funny Johnson was, albeit with a certain amount of editorial tempering. We remember why Johnson wouldn't go backstage at Garrick's theatre, what with the actresses exciting his amorous propensities and everything, but what he actually said was, "I'll no more come behind your scenes, David; for the silk stockings and white bubbies of your actresses excite my genitals." But we continually see Johnson smiling slyly, having fun with his own reputation, teasing those in awe of him and - eventually - apologising when he goes too far. It is something to be proud of, I think, to have as one of the central pillars of our literary history a man who can admit that he once tried knitting (or, as he most pleasingly puts it, "knotting"): "Knitting of stockings is good amusement. As a freeman of Aberdeen I should be a knitter of stockings." What does this mean? Is the joke on Boswell, or on us? And does it matter? Not at all - it's all part of the pleasure, along with the debate about whether it was true that Dr John Campbell once drank 13 bottles of port at one sitting.

There is one small problem. After extended immersion in this work, you begin to feel the poverty and glibness of much contemporary conversation. Johnson's circle knew how to enjoy themselves (even though Johnson himself was usually teetotal), but they also knew how to be clever; you can imagine them, transported to contemporary London, being appalled at what passes for wit and learning these days. I, for one, have become acutely conscious that I am not fit to look after Johnson's orange peel. But then, Boswell wrote about Johnson because he was extraordinary, and thanks to his devotion, we now have the most vivid portrait of an age - as well as a person - that has ever been published.

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