Curse that lasted half a century: New biography casts fresh light on Sylvia Plath's legacy

What could be more thrilling than finally having your debut novel published after years of honing your craft? Especially if it has been your goal since childhood; and the book is set to become not merely a modern classic, but a rite-of-passage read for every morose, misunderstood and proto-feminist teenager for years to come.

But for one young writer, publication, respectful reviews and a growing reputation were not enough; which is why early 2013 sees both the 50th anniversary of the publication of Sylvia Plath's sole novel, The Bell Jar, and of its author's suicide, which followed a few weeks later. Plath folded a cloth, placed it in her gas oven, and laid her head inside early in the morning of 11 February 1963, having first sealed the door of her children's bedroom. She was 30. "A doctor put her on very heavy sedatives – and in the gap between one pill & the next she turned on the oven, and gassed herself," her anguished, estranged husband, the poet Ted Hughes, wrote to a friend. "A Nurse was to arrive at 9am – couldn't get in, & it was 11am before they finally got to Sylvia. She was still warm."

To celebrate the happier anniversary, at least, there is a sparkling new edition of The Bell Jar, which has never been out of print, a series of events are planned for later in the year, and this month sees the publication of a major new biography, Mad Girl's Love Song by Andrew Wilson. In the past, Plath's hotly contested life has been a minefield for those who attempted to interpret it. "I tried to be as objective as possible," says Wilson. "I've got no agenda, I didn't read the other biographies, I went to the archives completely fresh, trying to stand back and see what kind of evidence there was."

He has conjured up a youthful, blonde and vibrant Plath, albeit one with a disturbing shadow side. But the dark fact of the suicide, on a bitter morning in one of the worst English winters on record, overshadows our understanding of the life and work of Sylvia Plath, and has cast something like a curse on the lives of those who survived her.

Hughes's letters in the months before the tragedy show no foreboding. He was, it seems, taken in by Plath's bright, capable manner, expressed in letters to her mother: "I am joyous, happier than I have been for ages," she wrote in October 1962. Her husband had been unfaithful with another poet's partner, Assia Wevill, and Plath had thrown him out with much drama and vituperation. Hughes was, if anything, relieved. "The one factor that nobody but quite close friends can comprehend, is Sylvia's particular death-ray quality," he wrote to his elder brother, adding that she was "finally, impossible for me to live married to. Now we're separated, we're better friends…" However, he also wrote to his sister Olwyn: "[Plath]'s changed extraordinarily – become much more as she was when I first knew her, & much more like her mother, whom I detest. You're right, she'll have to grow up – it won't do her any harm."

Alas, Plath was never to "grow up". "I was the only person who could have helped her, and the only person so jaded by her states & demands that I could not recognise when she really needed it," Hughes wrote to Olwyn after his wife's death. Crucially for the drama that was to unfold, the couple had only separated, not divorced. She was still Mrs Sylvia Hughes, and her literary estate was his to do with as he wished. He buried her in his native Yorkshire, under a slab that read "Sylvia Plath Hughes", and began the laborious business of sorting out her unpublished writings.

So famous is Plath now that it is hard to remember that like another poet who died young, Keats, all her renown was posthumous. Now her celebrity fans include such diverse figures as Gwyneth Paltrow, who played her in the 2003 movie Sylvia, and David Walliams. The poet laureate, Carol Ann Duffy, prefaced her recent selection of Plath poems with a fan-girl introduction, she has been name-checked in a Manic Street Preachers song, and copies of The Bell Jar featured in Natural Born Killers and The Simpsons.

But back then she wasn't an in-demand genius; the critic Al Alvarez was bemused to find that the dowdy, skinny American wife of the up-and-coming poet Ted Hughes was also a writer; he hadn't associated the housewife "Sylvia Hughes" with the Sylvia Plath whose poems were beginning to cause a small stir after her debut collection The Colossus (1960). There is a famous picture (below) of Ted Hughes with Auden, Eliot and Spender at a Faber and Faber party in 1960; Plath was at the same gathering, but she was not invited to join the great men. She has since arguably eclipsed them all, except Eliot.

Perhaps, given the position he found himself in, there is nothing Hughes could have done to forestall the criticism that was to trickle, then flood, in his direction. But giving his sister Olwyn the job of running the Plath estate on behalf of the two motherless children, Frieda and Nicholas Hughes, was not one of his smarter notions, given that the sisters-in-law had heartily disliked one another.

Literary estates are frequently contentious, as family members, sometimes not all that close to the deceased, attempt to control or even stifle biographers, critics and academics. Those who handle estates, and therefore permissions, are feared, needed and despised by biographers unless everything is handled with the greatest impartiality and transparency. The Plath estate was to generate huge revenues for the family. The Bell Jar alone has sold 400,000 copies worldwide over the past decade, and even today, Plath's publishers get five requests a week for permission to quote from her writing.

Hughes set to work. Instead of promptly compiling a Collected Poems, he constructed a new, slim volume of poems entitled Ariel, published in 1965. It was a masterpiece; but it did not exactly resemble the collection of the same name that Plath left behind. Understandably, Hughes removed several poems that were vengeful and critical about himself, and reordered the poems to suggest a narrative that made the suicide seem inevitable. (Plath's own ordering began with the word "Love" and ended with "Spring", giving a rather more optimistic flavour to the book.) Meanwhile, Plath became a heroine, or martyr, for the nascent feminist movement. Her gravestone was attacked, the offending "Hughes" hacked off more than once. Hughes, it was angrily put about, had as good as murdered St Sylvia.

Nevertheless, more material was appearing. Gradual revelation was also canny monetising. Uneasy about the autobiographical elements of The Bell Jar, Plath had published it under a pseudonym, Victoria Lucas. In 1965, it came out in the UK under her own name. In 1971, it came out in America, and in 1975, Plath's mother Aurelia brought out Letters Home, partly to counteract the harsh portrait of the mother in the novel. In 1977 came a selection of uneven but revealing short stories and prose pieces, Johnny Panic and the Bible of Dreams. Hughes brought out another slender selection of poems, Crossing the Water, and it was 1981 before the Collected Poems finally appeared, winning a Pulitzer Prize the following year.

Hughes also allowed the publication of Plath's Journals in 2000, although they do not cover her final breakdown. He confessed to having destroyed one journal and having "lost" another. Hughes did not want her children to have to read the last journal, he said. He retained the habit of talking about "the children" when they were well into their thirties, as though they remained frozen in time, forever crying in their upstairs room while below, the gas seeped out.

The biographers also set to work. The first, Edward Butscher, offended the family with unseemly speculations and revelations in Sylvia Plath: Method and Madness (1976), followed by Linda Wagner-Martin's feminist account, Sylvia Plath: A Biography (1987). In a preface, Wagner-Martin related how Olwyn Hughes, acting for Ted, demanded cuts of 15,000 words in exchange for permission to quote from Plath's poems. Wagner-Martin ditched the quotations rather than have her book gutted. Paul Alexander's Rough Magic (1991) was seen as even more objectionable.

The estate commissioned its own biography, authorised and overseen by Olwyn Hughes. It was a disastrous miscalculation. Anne Stevenson's Bitter Fame (1989) was harshly debunking, hostile to Plath and favourable to Hughes in all questions of the marriage. It was an extraordinary document to emerge from an estate that handled Plath's revenues. Bizarrely, three negative personal testimonies were added in appendices, one by Dido Merwin, a bitchy ex-friend eager to relate decades-old tittle-tattle. Reviewers howled and Stevenson confessed she had lost control of her own book, although the feminist critic Lorna Sage described Bitter Fame as "a good revisionist biography".

In The Haunting of Sylvia Plath (1991), literary critic Jacqueline Rose also recounted textual horror stories. Ted Hughes informed Rose that her speculation about the sexual subtexts of some of the poems would not only upset the children (again), but in some cultures, be "grounds for homicide", a shock tactic that, he later claimed, was not intended to threaten but to awaken.

As a result of all this, Janet Malcolm was moved to write a fascinating book-length essay on Plath, Hughes and biography, The Silent Woman (1994), landing broadly on the side of the Hugheses (although Olwyn comes across as a very strange person). Stevenson told Malcolm a tale of woe: Olwyn's constant revisions and comments had scuppered Bitter Fame. "Please respect my wish to be left in peace," Stevenson pleaded with Olwyn during the writing of the book. "No letters, no phone calls. You have brought me to the edge of breakdown many times in the past year." Another letter read: "A person can take just so much of being … kicked, insulted, threatened, bulldozed into submission…"

It's not surprising that people talked in terms of a Plath curse, and not just on biographers. No one suffered more than Assia Wevill, the beautiful and gifted woman for whom Hughes had left Plath. Fay Weldon, a friend of Wevill's, recounted in her autobiography, Auto da Fay: "Ted took up with Assia and made her pregnant, and Sylvia killed herself, and five years later Assia was to kill herself and her child, out of guilt from which Ted declined to save her." Appallingly, Assia also gassed her young daughter, Shura Hughes. The "Ted-Sylvia-Assia saga", Weldon wrote, "was I think one of those seminal events which brought forth the fruit of 1970s feminism. That such talented women should die for what – for love? Because that's what they died of, not depression, let alone 'born to suicide' as is so often said of Sylvia."

Says the poet and translator Elaine Feinstein, Ted Hughes's friend and biographer: "I think [Sylvia] and Ted were incredibly happy together, funnily enough, until she had her second child, and then she got rather tired and worn down. It doesn't help to have someone like Assia cross the path." The novelist Alan Sillitoe, a friend of the couple, once said vehemently to me: "I think Ted was a saint!"

I asked Andrew Wilson, Plath's latest biographer, whether time is finally healing all these wounds. After all, Plath's contemporaries are now in their eighties. Ted Hughes died in 1998, loaded with honours, finally redeemed by his heartfelt collection Birthday Letters – poems of love and contrition, addressed to Plath.

"I think it's still very, very raw actually," Wilson contends. "Understandably so. The latest thing is that Nicholas Hughes died." Tragically, in 2009, Nicholas Hughes, the baby Plath left behind on that freezing morning, killed himself in Alaska, aged 47.

"Anybody who's writing on Plath knows there are potential problems and difficulties. You have to be very careful," Wilson goes on. Although he encountered no problems with Olwyn Hughes. "She wrote me some wonderfully spiky letters," he laughs. "Obviously, she's one of the figures you come across many, many times in Plath studies, but I found her really easy to deal with. Very straightforward." Yes, I think Anne Stevenson would agree she's certainly straightforward…

Wilson focuses on Plath before she ever met Hughes, using vast archives held in the States. Wilson has noticed an odd thing: Hughes firmly insisted that everything she wrote before 1956 counts as juvenilia. "And it's when they first met! Nothing existed before in his eyes. I came across 200 poems that she wrote before then that have never been published, and lots of other items of archival material that have never been seen, and I've talked to friends and lovers who've never talked before, so it is an opportunity for a new, fresh approach."

His quest was urgent. A couple of his interviewees died shortly after he met them. "[Sylvia's friends] have reached an age when they think, actually, I would like to say something before I die. So it is a key moment, I think."

The cover of Wilson's book shows another side to a writer more often seen as death-struck than glamorous. "There's a huge archive of colour pictures that I discovered, taken by one of her boyfriends," he relates. "We picture her in black and white, don't we? We haven't really seen her in colour. We're used to seeing her with lank hair looking miserable! There are lovely pictures of her with blonde hair looking very vibrant."

Wilson found that he liked Plath and could empathise with her. "I know she was probably a very difficult person to be around but she had great charm, a great sense of fun. A lot of people who just read Ariel, which is terribly bleak, miss out on that. She was a very, very tortured individual and that's the source of her creativity, but I did grow to like her and I hope that comes across in the book."

Plath also reminded him of Patricia Highsmith, the subject of his previous biography. "Highsmith had similar symptoms to Plath – I don't know how you want to categorise it, but some sort of personality disorder or mental illness. Both of them were alive before people talked about those things, before anybody could classify exactly what they had. They both went through a great deal of soul-searching, both had therapy, which they wrote about in their journals, so it's fascinating to compare them. They both had very dark visions. But a crazy sense of humour at the same time."

One thing is certain: fascination with Plath's tortured life and magnificent poetry will continue, even as time heals the wounds left by a tragedy that has reverberated down half a century. "You couldn't help but feel sorry for Ted, because he wasn't the only man in London to commit adultery," says Elaine Feinstein wryly. "It's a great mistake to betray a poet."

'Mad Girl's Love Song: Sylvia Plath and Life Before Ted' by Andrew Wilson is published on 31 January by Simon & Schuster, priced £20. 'The Bell Jar' is published by Faber, priced £7.99