Henry Green is a writer who always seems to need "introducing", like a stranger at a party: dark, louche, awkward. It is odd, this need, because in his life he had friends enough, while his novels were viewed by people of dependable judgment as being among the best - perhaps the very best - of their time. Is it just that to later generations he is a little too "difficult"? Is it merely that Green requires a fraction more concentration than Greene? Perhaps so; but it is puzzling, this chronic shyness, when what his admirers are chiefly claiming for him is that he brings pleasure - a pleasure more intense, more original, more rewarding than that offered by any of his contemporaries.

Your first Green novel is in some ways your most memorable. I can still remember the incredulous pleasure with which I read Living in a battered library edition about 30 years ago. Here was a novelist who was doing something I had never experienced in fiction before. He seemed to have redrawn the familiar triangle between reader, writer and character, so that you somehow had the impression that you knew his characters better than he himself did. So real were they, so grand yet so fragile, that one felt protective of them - protective even against the plotting of the author.

Living (1929) is a story about people in a Birmingham iron foundry, most of them poor manual workers without much life beyond factory, family or a small terraced house. The absence of certain common words from the prose brings us face to face with the concrete nature of their world: harsh, hard to mould, monotonous. Yet alongside this machine-age view of the "masses", something underhand is going on. To begin with, it is in a kind of tenderness that Green allows to colour his descriptions; though when this feeling threatens to swell, he usually deflates it: sometimes our love for the people in the book seems unrequited - by them or by their author - and this can be painful. You vow not to fall so easily next time; yet soon the beguiling rhythms of the prose begin to seduce you once again, so that you long for emotional release, either within the fictional lives of the characters or in your unstable relationship with them. The inner shape of the novel in this way imitates our experience of living: it promises pattern, then withholds it, insisting on a formless banality; it describes intensity, but as part of a grudgingly accepted monotony; it glimpses poetry, but only from the corner of its eye.

Green came from a wealthy family, was educated at Eton and Oxford and knew many of the people whose names are familiar from literary biographies of the period. His "research" for Living was undertaken while he worked for his father's company, which made plumbing supplies and beer-bottling equipment in a factory similar to the one described in the book. His attentive, unpatronising attitude to the working-class characters was cause for comment when the novel came out, in 1929, as was his largely satirical treatment of their employers. Green, however, had grander interests than those of "class". Most of the workers are idle or conniving, and while the toffs are epitomised by a young man who can do tricks with a glass of water without spilling it on his dinner jacket, they also have their complications, their light and shade. Young Dupret, the factory owner's son, may be a secret nose-picker, but he does see beauty in the work the men do.

Green hardly ever gives psychological accounts of his characters, their motives, childhoods or formative experiences. In this respect Green seems to belong to the Modernist movement, which preferred its depiction of reality broken up into its constituent planes, like Picasso's, or fragmented, like Eliot's. What makes Green distinctive, however, is that despite following the manner of his time, he is able to convey, in Living for instance, such a warm sense of what old Mr Craigan, or the talented but shifty Tarver, or Lily Gates, bursting to be a mother, is really like. One of the book's greatest passages is the attempted elopement of Lily and Bert Jones to Canada, which takes them no further than Liverpool. In a scene that is comic and moving at the same time, one sees these human fragments move from one urban mass to another, then falter under the weight of their own insignificance. Even the story seems unable to bear it. "What is a town then, how do I know? What did they do?" asks the narrative. Even at this self-consciously literary moment, one never loses sight of Lily in her childish desire to escape, so easily deflated, or Bert forced by his wounded bravado to abandon his lover when he cannot even track down his own parents.

Green wrote his first novel, Blindness (1926), when he was 18. It is a book of astonishing maturity for one so young, yet it is Living that is the triumph of his precocity: a near-masterpiece written at the age of 24. Of the three novels in this volume, Party Going (1939), though it has proved a most fertile ground for critics and theorists of narrative, is the one that is most likely to be problematic to the non-academic reader. Nothing much happens, and the characters are all more or less appalling. Frank Kermode has written that the way most contemporary readers see this novel is as "an expression of disgust at the conduct of the immature, ostentatious rich ... and of admiration, even tenderness for the poor".

This is not at all the way I read Party-Going. Green was a naughty man in some ways, and occasionally his naughtiness gets into the books; usually it appears as a playful teasing of the reader (he likes characters to be known by different names: Mrs Henderson is for no clear reason both Evelyn and Evelyna; Angela Crevy is known by both her names); and generally one feels that his is an attitude like that of Shakespeare in his comedies: the world is an absurd mess, you cannot blame me if in our enchanted wood there are two men called Jacques. Green talked in interviews about getting a "dig" in at various real people and at the aristocracy in general, and doubtless he took some small pleasure from exactly that (his stern father is guyed in the figure of old Dupret in Living). But the artist in him was above the drab politics of 20th-century class warfare. For Green is a plotter - not in the sense of someone full of narrative surprises - but in the manner of a spider with a web in which these flies are caught and then inspected.

Party Going is at pains to point out the shallowness of its characters ("Robin ... wondered angrily how Angela could go with these revolting people"), but its artistic purpose is surely more ambitious than that of social criticism. Green, in his youth, was an addicted cinemagoer, and much has reasonably been made of his cinematic technique: the short, flickering scenes, the jump-cuts and so on. However, a more helpful, if necessarily approximate, analogy is with music. Living must, I suppose, be a symphony by an "avant-garde" Russian, though with more melody than that comparison perhaps suggests; Loving could be a collaboration between Britten and Vaughan Williams; but Party Going is pure chamber music. This is amoral virtuosity, unashamed, self-regarding in places, dizzy with its own patterns of invention.

Can you tell the difference between Angela and Claire and Julia and Evelyn? Does it matter? Isn't part of the point that such people are, ironically, just like the "masses": indistinguishable one from another? Does Max prefer Angela to Amabel[sp?] or Julia to both? In fact, how can he be sure, when they are almost interchangeable? Who is this man with the mysteriously shifting accent who shuttles to and forth between the hotel barred against possible "revolution" and the foggy underworld outside? What is the function of the dead pigeon and why does Miss Fellowes feel she has to wash it?

At times it seems that the people in Party Going are like characters from a Robbe Grillet novel, from whom individuality has been withheld as a matter of literary dogma; and yet they do have individual characters, even if what distinguishes them (different amounts of money, different degrees of familiarity and affection for one another) is not profound.

The climactic interchange of the book, it seems to me, is between the lovers Max and Amabel, who have been deceiving and avoiding one another throughout and continue to do so when face to face. She pulls at her handkerchief, threatening tears; but he "hated tears, he never found them genuine". Never! A few moments later, she "made her eyes cloud over", and we do not know if she is truly sad or not - and neither, perhaps, does she. As real feeling eddies beneath the surface of brilliantly simulated emotion, Green begins to see what dialogue, unmediated by a narrator, can achieve; his interest in this technique was to take him in one of his final novels, Nothing, into a rather austere place, where fewer readers wanted to follow. Here, however, between Max and Amabel, the effects are sublimely minimal; it as though a scene from Private Lives has been revised by Samuel Beckett.

Party-Going is not as easy to love as Living is, but it is impossible not to admire its artistry. Of these three novels, Loving (1945) is perhaps the most immediately sympathetic to a contemporary reader. We are in the aristocratic setting of Party Going, but it is the servant class of Living who are the main characters in a largely below-stairs comedy of life in an Irish country house during the second world war. The erotic manoeuvrings and duplicity of the servants are given to us with some of the stylistic quirks of Living - the ellipsis, the omissions of articles and so on - though here this quirky grammar serves to depict not a factory but a mansion of closed rooms and quiet corridors where people are often surprised by the unheard approach of others; stables where an idiot lampman lies asleep; and gardens where the air is rent by the screech of peacocks.

Another important difference about Loving is that, in a quiet way, a great deal happens. In Romancing, his admirably concise, no-nonsense biography of Green, Jeremy Treglown's summary of the action runs over three pages. I also feel that the main characters in Loving are more fully developed psychologically than Bert, Lily, Craigan, or young Dupret in Living, or than any of the party-goers. Green still offers little in the way of "back-story" and retains a distrust of "motivation", but somehow we do become familiar with the nature of Charley Raunce, the venal, nervous head footman, surprisingly promoted to butler, and of Edith, the ravishing, gentle but conniving underhousemaid.

Green clearly loves this girl, and we can forgive him for doing so. The delicacy of her nature is beautifully given, in her consolation of the old head housemaid Miss Burch, in the modesty of her blushes, in the sensitivity that causes her to shriek then faint at the sight of a trapped mouse (though her faintness is perhaps also caused by the hysteria of her suppressed desire for Raunce) and in the natural and loving way that she plays with her employer's granddaughters, Miss Moira and Miss Evelyn. Indeed, the game of blind-man's buff between Edith and the children in an abandoned room of the old castle is one of the great lyrical scenes of the novel.

This writer is unique. No fiction has ever thrilled me in the same way as the great moments in Living and Loving; I have been moved by Tolstoy, Lawrence, Proust and others, perhaps more so, but not in the same way. Interviewing him once, the American Terry Southern, while ostensibly writing about a number of internal inconsistencies in Green's plots, described this singular quality quite well, I think:

"The reader does not simply forget that there is an author behind the words, but because of some annoyance over a seeming 'discrepancy' in the story must, in fact, remind himself that there is one. This reminding is accompanied by an irritation with the author for these apparent oversights on his part, and his 'failings' to see the particular significance of certain happenings. The irritation gives way then to a feeling of pleasure and superiority in that he, the reader, sees more in the situation than the author does - so that all of this now belongs to him. And the author is dismissed, even perhaps with a slight contempt - and only the work remains, alone now with this reader who has to take over. Thus, in the spell of his own imagination the characters and story come alive in an almost incredible way, quite beyond anything achieved by conventional methods of writing."

Henry Green's writing life was sadly short. He drank too much, worried about money and found the effort of producing these complex, touching works of art too much to contemplate after middle age. He wrote an early memoir called Pack My Bag, published in 1940, when he was only 35. In a passage that begins as no more than a reflection on the memoirist's difficulty in using the real names of people he has known, he goes on to talk about what writing is, or should be. His definition is one that I - and, I expect, many other admirers - have long had pinned above the desk:

"Prose is not to be read aloud but to oneself alone at night, and it is not quick as poetry but rather a gathering web of insinuations ... Prose should be a long intimacy between strangers with no direct appeal to what both may have known. It should slowly appeal to feelings unexpressed, it should in the end draw tears out of the stone ..."

· This is an edited version of Sebastian Faulks's Introduction to the single-volume edition of Living, Loving and Party Going by Henry Green published by Vintage. To order a copy for £9.99 with free UK p&p call Guardian book service on 0870 836 0875.