In the afterword to his translation of Jakob Wassermann's My First Wife, Michael Hofmann quotes Rilke: "In the depths, everything becomes law." The divorce of man and woman is one such depth, an anti-tale of many inversions: love becomes hate, unanimity becomes animosity, shared interests become competing claims, alliance becomes war; and everything that seemed fleshly and human and natural, everything for which it might appear impossible to legislate  trust, generosity, self-sacrifice, nurture, belief itself  everything does indeed become law.

Wassermann (1873-1934) wrote this account of his divorce from his wife of 20 years  a work of "exactest, most scrupulous autobiography"  at the end of an exhaustingly prolific writing career. His oeuvre is now almost entirely forgotten, but in his lifetime he was a celebrated novelist, an associate of Thomas Mann, and like Mann was one of what Hofmann describes as "the first commercially successful generation [of writers]; they made writing look like a reasonable career option." With their cars and villas and servants, their antiques and their foreign travel, they dispensed with the idea of the artist as unmaterialistic and free; creative prestige was translated into the solidly bourgeois appurtenances of life and the middle-class values of encumbrance.

Some great art was the consequence of what might be called the elision of artist and patron in the dawn of the 20th century, for as Hofmann notes, successive bourgeois generations "[were becoming] cultivated and even a little neurasthenic themselves". The novel, an increasingly bourgeois form, gained a more dynamic relationship to its own material; but the artist's management of "normality", of marriage and mortgage and school fees, became a new source of pressure and creativity. According to this theory, writing becomes both more bourgeois and more personal; and the bourgeois, personal experience of marital breakdown is what My First Wife is all about.

Wassermann was a German Jew who went as a young man to Vienna, where he met and married Julie Speyer, one of six daughters of a wealthy and privileged family. Wassermann's childhood had been chaotic and harsh; he was unschooled in the kinds of constructions that might attend a middle-class girl's notions of marriage and home. She, on the other hand, was fixated by the idea of the artist  Wassermann had just published his first novel  as something that might be possessed and lived through. She appeared to offer him financial security; and he, despite some mild breast-beating over selling his soul, entirely failed to see what it was being sold for, or to whom. Before long he found himself living in suburban Vienna on limited means  the dowry having quickly been spent  with a wife and small children; and it is here that normality, and the question of the artist's management of it, begins.

My First Wife uses the names of Alexander Herzog and Ganna Mevis for its protagonists, though it adheres down to the last detail to Wassermann's own experiences and takes the form of a long, spoken confession. Wassermann was sick and beaten when he wrote it in 1933, and died before it was published the following year. And it is indeed the story of his undoing, to the very death, not just by the woman he married but by the institutions to which he gave himself over by marrying her. "I was always," he writes at the beginning, "stood so close to reality  like a man working at a machine, in front of its wheel  and yet I didn't see it. I exhausted myself in the effort to see it, but the pictures I saw, the experiences I had, were utterly transmuted by the galvanic process that befell them in my imagination. Something light became heavy, something cheerful became murky, warnings found me deaf, even pain and joy were like two puffs of breath on a sheet of glass  The need to act concussed my entire being, shooing my soul up out of its remote hiding place, and demanding it set out on a hundred-mile march."

The need to act comes upon Herzog/Wassermann after two decades of marriage, when he meets and falls in love with a woman  Bettina Merck  through whom reality becomes finally, startlingly visible. She divorces her own husband with comparative calmness and speed, and expects that he will do the same; but Herzog, who for years has existed frankly and miserably captive to Ganna, who has trumpeted that misery in numerous infidelities, who is able to be honest with himself and others about the unhappiness of his marriage, cannot free himself and survive. "Observation is so utterly different from experience," he writes. "There is no hope of fusing their contradictions, as the I and the not-I have been foes from the world's beginning." In a sense, marriage is the human attempt to fuse the "I and the not-I" and divorce an exercise in the ultimate irreconcilability of point of view.

What Herzog doesn't realise is that through marriage, however much he hated it, he had access to universality: the "I and the not-I" were bypassed in favour of a third thing, the "it". In marriage his galvanic process could work on undisturbed, transmuting and interpreting; but in divorce he is forced to externalise that process so that its power is broken. Artistic perception becomes just a point of view, individual truth merely "the truth of [one's] own narrow perspective".

The Herzogs' divorce becomes a middle-class appurtenance indeed: when Alexander finally leaves, the vast machinery of Ganna's institutionalised assumptions, her bourgeois will to power, cranks into action. She deploys teams of lawyers, issues writ after writ, and ties Alexander up in so many knots of alimony and maintenance that his writing becomes not just a reasonable career option but wage slavery. Far from revering the writer, she wants, in fact, to destroy him; now that his freedom, his honesty, have become actualised, she despises them, for they interfere with her will. And Alexander, on his side, finds that he cannot dispense with the bourgeois ideal of marriage so easily after all. He is traumatised at the thought of what he has broken. He can't deal with Ganna forcefully, not because he loves her but because he is frightened of having offended her gods. Her ceaseless suits against and harassment of him continue unabated and fury-like until the book's end.

The candour and extremity and intelligence of My First Wife are profoundly affecting, for they serve and honour their subject: Wassermann does it justice, the catastrophe that is the separation of one human being from another, the breaking of what "even now, even now" he half-believes to be "mystical union". This is a literary masterwork of a vanished kind, but through the remarkable Hofmann it is born again as a story for our age. Hofmann has the rare ability to refresh the very heart of a text in translating it, to increase its connections to life. And this is a text whose moment has come, because it wins by the route of art so many of the arguments in which the memoir form is bogged down, whereby personal truth is invariably demeaned as "dirty laundry". Were Jakob Wassermann still alive, he would doubtless suffer for it; that torment, at least, he has been spared.

 Rachel Cusk's Aftermath: On Marriage and Separation  is published by Faber.