It shames me to admit that I came somewhat late to Henry James. In my adolescence I read The Turn of the Screw and, being young, largely missed the sly and appalling ambiguities of this ‘trap for the unwary’, as James himself described the novella – is it a ghost story, or a study in hysterical mania? I found the style overblown and precious. Later on, when I was well into my twenties, I at last heeded my wife’s urgings and took a copy of The Portrait of a Lady with me on a family holiday to Italy, which started out in Venice, proceeded to Florence and ended in Rome.

It was in Florence, in an endearingly dingy little hotel on the Via della Scala, close by the Basilica of Santa Maria Novella, that I read the first chapters of The Portrait of a Lady, the great masterpiece, as I discovered, of the Master’s middle period. What I did not realise at the time was that, by happy coincidence, in my lodgings on the Via della Scala I was not far from the site of the hotel on the Arno where James embarked on the composition of the novel in the spring of 1880 (in the preface to the much later and much revised New York Edition he gave the year, erroneously, as 1879). Additionally, just round the corner from my hotel was the building on the Piazza Santa Maria Novella where, later on, James rented a room to continue work on the novel, which, in reply to William James’s querulous demand for more ‘fatness and bigness’ in his brother’s work, Henry promised, or perhaps a better word is threatened, ‘shall be big’.

The Portrait of a Lady opens, with a famously leisured flourish, at a tea party on a sunny summer afternoon on the lawn at Gardencourt, the country home of a wealthy American family, the Touchetts. There is Daniel Touchett, the placidly dying paterfamilias, Lydia, his curt, cold wife – who, despite all her efforts, turns out to be one of the most vivid figures in the book – and their son Ralph, ‘tall, lean, loosely and feebly put together’, with an ‘ugly, sickly, witty, charming face’, who is a consumptive and, like his father, stoically dying.

It is here that we first encounter Isabel Archer – framed, appropriately, in a doorway – in a quintessentially English scene, but for me, as surely for many of his readers, this is Henry James’s ‘Italian’ novel, the one in which he expresses with deepest tenderness his love for that exquisite, history-haunted, irredeemably decrepit and impossible, loveable country.

After beginning the book in Florence, James carried it on, the following year, ‘during a stay of several weeks made in Venice’, where he had rooms on Riva degli Schiavoni with a view over the Lagoon. Many writers have tried their hand at capturing the unique aspect and atmosphere of that magical floating city, but no one brought it off as successfully as Henry James. He was very well aware of the danger, for the novelist, of succumbing to the merely picturesque, in which Italy so amply abounds, and in the pages of the novel he is careful to avoid tourist-brochure gush; even when, in the preface to the New York Edition, he lets his memory wander fondly southwards, it is not scenes from the book’s fictional life he lights upon, but recollections of his own circumstances when he was writing it: ‘There are pages of the book which, in the reading over, have seemed to make me see again the bristling curve of the wide Riva, the large colour-spots of the balconied houses and the repeated undulation of the little hunchbacked bridges, marked by the rise and drop again, with the wave, of foreshortened clicking pedestrians. The Venetian footfall and the Venetian cry – all talk there, wherever uttered, having the pitch of a call across the water – come in once more at the window, renewing one’s old impression of the delighted senses and the divided, frustrated mind.’

Anyone even slightly acquainted with Venice will recognise those ‘foreshortened clicking pedestrians’, who are still there, even as the poor old city, squatting on its piles, is being sunk by the ever-swelling ‘Venetian footfall’ and the backwash of the vast holiday liners that in recent times the city authorities, even more stupid and venal than in the days of the doges, have disastrously allowed to anchor in the Lagoon.

Most readers of The Portrait of a Lady, when they have been away from the book for a while, fall back into the notion that James’s heroine, self-willed and naive but stalwart for all that, is undone by wily and wicked Europeans. This is not the case, however. Madame Serena Merle, who manoeuvres Isabel into a calamitous marriage, is the daughter of an American naval official and was born in Brooklyn, of all places; her former lover, and Isabel’s husband, the ‘sterile dilettante’ Gilbert Osmond, is a native, though long exiled, of Baltimore. From the start, Isabel is surrounded, indeed is crowded in upon, by her fellow countrymen and countrywomen. The one leading character who is genuinely English, the wealthy and well-meaning Lord Warburton, when he offers Isabel his hand in marriage has it immediately and brusquely handed back to him.

The book, therefore, is an American drama played out among American characters against a European backdrop. We might say, however, that they have all been tainted, and in some cases corrupted, by Europe, or at least by what Europe represented – paradoxically, perhaps – for the unfailingly Europhilic James: a place, a milieu, tender, lovely and enviably cultured, which yet is sick at heart, and sickens the hearts of those who fall for its all too plausible charms. Ambiguity, as we know, is the essence of James. T S Eliot wrote of Webster that he was one who saw ‘the skull beneath the skin’. Henry James, when it came to Europe, saw the sin behind the splendour.

I return again and again to The Portrait – I recently gave a series of classes on it at the University of Chicago – and my intimacy with the novel is now being intensified by the fact that I am, with all the arrogance and foolhardiness for which I am infamous, writing the sequel to it… Perhaps I should go back to Florence and write it there.