James Wood sees literary criticism as a means of revealing truth in novels � and exposing phoneys

Kenneth Tynan, the doyen of theatre criticism, once said: "A critic is a man who knows the way but can't drive the car." Certainly, nobody, not even Tynan, became a critic in the expectation of receiving bouquets. Most writers have about as much affection for them as they have for head lice. But in an age when anyone with an opinion, however ill-informed or ignorant, can preserve it in print, post it on the internet and reach a receptive audience, the need for critics who can bring their authority, experience and perception to bear on works of art and articulate what makes them great or tat has never been more urgent.

James Wood is one such. Recently appointed a staff writer at The New Yorker and the professor of the practice of literary criticism at Harvard, he is arguably the world's leading critic, devoting his career to the study of fiction. Writers as diverse as Susan Sontag, Harold Bloom and John Banville have attested to his ability to burrow beneath the skin of a novel, showing why it is less - or more - than the sum of its parts. Like all the best critics, Wood is as dispassionate as a surgeon and as enthusiastic as a child with the latest gizmo. Whether he praises or pillories, he makes you want to read the text he has freshly filleted.

Though born in Durham in 1965, Wood - had he been a footballer - would have been eligible to play for Scotland on account of his Skye-born mother. With her husband, a zoologist, she has retired to the Borders and Melrose. It is here that, one sleaty January morning, I catch up with Wood, who is at home for a fleeting few days. His latest book, How Fiction Works - published next month - is a provocative, scholarly triumph which ought to be required reading for authors, readers, reviewers, students and teachers of the novel, as well as anyone who aspires to write fiction.

As Wood himself - a slim, balding father of two young children, who is married to the acclaimed American writer Claire Messud - acknowledges, such books are surprisingly few. In his introduction, he mentions as kin EM Forster's Aspects Of The Novel, which first appeared in 1927, and Milan Kundera's three volumes on the art of fiction. But neither of those authors' books is quite like Wood's.

"In this book," he says, "I try to ask some of the essential questions about the art of fiction. Is realism real? How do we define a successful metaphor? What is a character? When do we recognise a brilliant use of detail in fiction? What is point of view, and how does it work? What is imaginative sympathy? Why does fiction move us?"

All of which may appear pretty basic but, as Wood demonstrates, even well-known novelists seem to struggle to understand what the mechanics of their job is and how to go about it.

Take realism, for instance. Wood cites American novelist Rick Moody, who says the realistic novel needs "a kick in the ass", as "it's politically and philosophically dubious and often dull". This, argues Wood, is nonsense, and based on a misunderstanding of what realism actually is and what the novel's relationship to it is. While novels may appear realistic, they are still novels - artifices, whose reality is that which the novelist chooses to present to us.

Great novelists, says Wood, such as Flaubert or Henry James or Saul Bellow, offer their readers a world in which "reality" is not a mirror of the "real" world but of their manufacture. Bad writers do not appreciate this, for "they assume that the world can be described".

"In America," Wood adds, "the battle lines are more fiercely drawn up than in Europe because of the tendency on the realist side to be somewhat anti-intellectual and masculinist - that whole sort of post-Hemingway line. A writer I admire, like Richard Ford, say, would probably be thought of by people like writer and academic David Foster Wallace as prehistoric, unintellectual. I don't think that's fair. But there has been a tendency in American writing schools to enforce a slightly unthinking realism. Someone told me that at Iowa Writers' School a few years ago author Frank Conroy used to hand all incoming novelists a copy of Madame Bovary, saying, It's all in there. That's all you need to do'."

Another area of conflict for Wood is character. Log on, he suggests, to sites such as Amazon and read how common readers - as they used to be called - react to novels and their characters. Here, Wood detects "a kind of moralism" going on. "Again and again, people say, I don't like the book because I couldn't identify with the characters in it.' How many decent characters are there in fiction anyway?"

By way of illustration, he mentions Muriel Spark's The Prime Of Miss Jean Brodie, the only Scottish novel considered in How Fiction Works. "What does it mean to love' a fictional character," he asks, "to feel that you know her? What kind of knowledge is this? Miss Jean Brodie is one of the best-loved novelistic characters in postwar British fiction, and one of the very few to be something of a household name. But if you dragged a microphone down Princes Street in Edinburgh and asked people what they know' about Miss Brodie, those who had read Muriel Spark's novel would likely recite a number of her aphorisms: I am in my prime', You are the crème de la crème', and so on. Miss Brodie, in other words, is not really known' at all. We know her just as her young pupils knew her: as a collection of tags, a rhetorical performance, a teacher's show."

To the business of criticism, Wood brings his personal baggage as a self-confessed Presbyterian Calvinist. He is a seeker of truth and enlightenment, reading being a sublime form of communication, an act almost of religious application, which requires serious study if its rewards are to be properly mined. What he is always on the lookout for are phoneys, bum notes, intrusive authorial voices, obviousness, lazy thinking, the denial of art, the fear of experiment. Iconoclastic he may be, but he is also respectful, sensitive and challenging. As he sees it, he has a moral imperative to investigate hype and hypocrisy, showing readers less well-read than him in every sense what is actually going on in a novel.

"When I was writing about Tom Wolfe, reviewing A Man In Full," he says, "it seemed to me there was a moral and aesthetic task as a critic: to say to the reader, now, he keeps on saying he's like Dickens. First of all, let's have a look at Dickens. Secondly, if you believe that he's as good as Dickens or that he will give you the sustenance that a really good novelist - Philip Roth or Bellow or whatever - can give you, then you're cheating yourself and you're being cheated, and I'm going to point out how he's sentimental, raucous and crude."

And, Wood adds, if what he's got to say reaches the ears of readers' groups so much the better. For reading, like writing, is all very well. But reading intelligently is another thing entirely.

How Fiction Works, Jonathan Cape, £16.99