The notoriously grouchy novelist John Fowles was generous in one thing - the sheer volume of his complaints. In the second instalment of his Journals, edited by Charles Drazin, his stellar career is "a millstone round my neck"; his devoted wife "a corpse, a talking corpse, on one's back"; humanity at large "a sick race on a sick planet". When his step-grandchildren arrive for Christmas, their high spirits prove an intolerable insult to Fowles's morose equilibrium: "the egocentricity and wilfulness of modern children is terrifying", he writes. "I want to be alone."

Such Garbo-esque gloom was a private counterpoint to a gilded public existence. By the mid-1960s, when this volume opens, Fowles was a literary superstar with The Collector and The Magus behind him, and his status was confirmed by the publication of The French Lieutenant's Woman in 1969. Conceptually tricksy and sexually frank, his novels were required reading during the 1960s and 1970s, piled on every self-respecting hipster's mantelpiece alongside Zen and the Art of Motorcycle Maintenance and R D Laing. The first half of the volume traces an inexorable crescendo of suc- cess: in March 1977 an advance for Daniel Martin and the film rights to The French Lieutenant's Woman earned Fowles half a million dollars in one week.

For ten years or so, Fowles lives the life of a millionaire author - and resolutely fails to enjoy it. He flies ("it is uglier than any other way of travelling in the history of man") frequently to the US to meet his agents, attend parties in New York and discuss film treatments in Miami and LA. He meets Michael Caine, who stars in the film adaptation of The Magus ("a thoroughly unlikeable young man"), Twiggy ("the latest idiocy in the fashion world"), Terence Stamp, Saul Bellow, Harold Pinter and Antonia Fraser. He wins the W H Smith Prize ("I loathe the publicity") and refuses election to the Royal Society of Literature: "I looked at some of the names of those elected before me, and declined the honour."

These acid annotations to the literary high life provide the Journals' rare mo-ments of (sour) fun. When, in a moment of frivolity, Fowles accepts a commission from the "egregious" Cosmopolitan, he is horrified to receive instructions to profile Raquel Welch and Vanessa Redgrave "from the ordinary virile man's view". He is put out when a Sunday Times journalist likens him to "a badger pursuing its undergrowth paths" - "I should have hoped to rate at least a buzzard to his peregrine". And there is a stiletto-sharp sketch of the 1971 Booker Prize panel, on which Fowles sat alongside Bellow and Philip Toynbee:

The others come, we sit to lunch. Bellow declares himself anxious to get it over and done with. A little flurry of British horror at this American brashness. Toynbee suggests perhaps we wait till coffee, in that lovely English voice that is outwardly exquisitely polite and inwardly tells you you are a bloody fool. Dangerous - Bellow has a long nose.

But unlike his publisher Tom Maschler (whose celebrity-struck memoirs were published last year), Fowles isn't a gossipy diarist by inclination. After 1980, the literary parties and starry acquaintances disappear as he retreats to Lyme Regis to brood on a litany of imaginary disasters, from minor illnesses to the vileness of his neighbours ("the most abominably retarded community one can imagine"). As his life unravels, long-running battles with his wife Elizabeth, "Eliz", intensify. "We walk a tightrope over hell," says a typical entry. It makes for gruelling reading, brightened only by his occasional pleasure in the company of orchids, fossils or 18th-century pamphlets. After so many fake calamities, Elizabeth's death from cancer, which closes the volume, feels oddly unreal: "I can't believe it, it's not happening," she says when Fowles tells her the diagnosis. "It can't be true, it can't have happened," he writes later.

It's a sad end to the tale of a man used to manufacturing his own misery. Despite the supple precision of Fowles's prose, the Journals are so bile-drenched that an isolated moment of compassion provides their biggest shock. "I feel sympathy for him," he writes when Evelyn Waugh's vitriolic diaries are serialised in 1973. "One can forgive such a sharp eye and such a trenchant, pruned style almost anything." While it's hard not to read this as Fowles's hoped-for verdict on his own diaries, it is harder not to read his assessment of Philip Larkin - that he wasted his talent on becoming "our greatest depresser and putter-down" - as the more accurate one.