"Any modern reader of his work must be struck by its practicality," Taylor encourages us. "He is one of the few Victorian novelists from whom you could find out how to order a dinner or discount a bill, and in `Memorials of Gourmandising' he produced an extended version of the modern restaurant column."
Yes, but what else? His point is more subtle than it seems. We can read Dickens without knowing a thing about him. Thackeray, as Taylor makes clear, is the opposite kind of writer. Hence the Interlude.
When William Makepeace Thackeray was a boy at Charterhouse he was amiable, middle-sized and unremarkable. By the time he got to Cambridge, he had grown to six feet three. A school friend called Venables had broken his nose, making it comically bridgeless. His face was further distinguished by a monocle.
No one he met at Trinity College supposed he would amount to anything. Why should he? He came from a good family and, if he followed the advice of his pious mother and good-natured stepfather, he could live quite comfortably doing nothing very much.
In other words, he was a young gentleman of independent means. Two things happened to him that changed his life. He gambled away his inheritance and he married the wrong girl.
By the time the 18-year-old Victoria became Queen in 1837, Thackeray - aged 24 - was scratching around in rooms in Great Coram Street, writing for money. The change was as dramatic as his childhood increase in height. The jolly, gentle giant had all but fallen over the cliff.
His journalistic forte was the sketch and the facetious lyric. At one time, he had wanted to be an artist. Taylor's text is generously supplied with Thackeray drawings - but, like the stuff he was knocking out in prose, they are faintly grotesque. Or perhaps we can see in them a hesitancy, an unwillingness to go all the way. Thackeray knew he was endlessly compromising his amateur and gentlemanly status. Unlike Bulwer Lytton, one of his favourite literary targets, he wrote to eat.
His wife, who was barely more than a child when he married her, went slowly mad and was eventually hidden away. (She outlived him comfortably). His two surviving daughters were farmed out with grandparents. He himself lurched from one financial crisis to another. And then came the miracle of Vanity Fair.
Thackeray was 36 when this wonderful book began to rise from the comparative dross of The Snobs of England (with which it overlapped slightly in serial form). He knew he had something exceptional under his hand while he was writing it, but its success both made and destroyed him.
From now on until his death, Thackeray's fame and fortune was assured. But he would never write as well again - a fact Taylor brings out skilfully and in great detail.
What was left of the writer was the man - worse than that, the celebrity. Even though he had devoutly wished this situation on himself, he could not now comfortably come to terms with it. As Yeats said, the quarrel you have with others is rhetoric. Only with yourself is it poetry.
This new biography is very good on money and excellent on the gloomy trade that is ephemeral publication; the same then as now. Taylor devotes a chapter to the famous row with the unfortunate hack Edmund Yates, which became all too swiftly a bitter quarrel with Dickens and the basis of The Garrick Club Affair. Though Thackeray was never spiteful, he could be pompous - and very often emotionally obtuse, something which the book teases out of his relationship with the Brookfields.
While he was still in the throes of loving Jane Brookfield, his friend's wife, he wrote this to her from Brighton, having just read the reissue of The Great Hoggarty Diamond. "And after all I see on reading over my book, that the woman I have been perpetually describing is not you nor my mother but that poor little wife of mine, who now does not care 2d. for anything but her dinner and her glass of porter."
This is not an ideal statement of love in any situation, but is gross in the context of Thackeray's more or less total abandonment of poor Isabella. Nor, as Taylor points out, does it help his case that when Jane went into labour with the Reverend Brookfield's child, Thackeray was only finally ejected from the house a quarter of an hour before the birth. He came to believe in the end that Jane Brookfield had been making fun of him, which is almost as ghastly as the way he could be said to have toyed with her.
On the other hand, he was a friend as well as a father to his children, who adored him. In the not very demanding ambience of the Garrick and the Punch table, he could be witty and entertaining, but never quite as successfully as he supposed. Like his perceived rival, Dickens, he worked incredibly hard. Taylor brilliantly chronicles his subject's slow disillusion with a business he could not leave alone. In so doing, he may occasionally put aside a little too much the quarrel Thackeray had with himself.
Happily, there never was and never will be one Thackeray. His contemporaries understood that, for his satirical strength was directed at the very thing they feared most - not the momentary loss of their dignity, but the almost wholesale demolition of their sense of class. In supposedly more classless times we ought to be able to pin Thackeray down, yet he continues to discomfort us as much as he delights.
D J Taylor's exhaustive biography has surely assembled all the facts we need to make a judgement. It's a sign of Thackeray's genius, and his tenacious hold on common human anxieties, that the jury is still out.
Brian Thompson's book `A Monkey among Crocodiles' will be published next year by HarperCollins
by D J Taylor
Chatto & Windus, pounds 25, 478pp