A novel written by the Colombian Nobel laureate Gabriel García Márquez in the last years of his life has been published – against his instruction that it be destroyed. Until August, written when the author had dementia, comes a decade after his death, on what would have been his 97th birthday. It has been described by his sons as “the fruits of one last effort to carry on creating against all odds”, and tells the story of a woman who makes a yearly pilgrimage to her mother’s grave on a Caribbean island, a trip that becomes dominated by a series of chance sexual encounters.

In the face of increasing memory loss, García Márquez – known as “Gabo” – lost confidence in the work before his death, and asked for its destruction. Until now, the manuscript has been available to scholars at the writer’s archive in the Harry Ransom Center in Texas, but recently the author’s sons Rodrigo and Gonzalo García Barcha made the decision to publish it, judging it to be far better than their father believed. “In an act of betrayal,” they write in their introduction to the novel, “we decided to put his readers’ pleasure ahead of all other considerations. If they are delighted, it’s possible Gabo might forgive us. In that we trust.”

Speaking from his home in Mexico City, Gonzalo García Barcha conceded that it was “hard to go against the grain” of his father’s wishes, but insisted that there were “plenty of examples in the history of literature of people who are requested to destroy manuscripts, and then they turn out to be important items in literature. For me personally, it’s a relief in the sense that this is actually the last piece Gabo wrote. I feel that his complete works would be unfinished if this wasn’t published. There are no other novels hiding around in Gabo’s papers.”

García Márquez rose to global prominence as the author of novels including 1967’s One Hundred Years of Solitude, The Autumn of the Patriarch (1975) and Love in the Time of Cholera (1985). He is widely regarded as one of the most influential writers of magic realism, in which fantastical and supernatural elements blend with evocations of everyday life. In One Hundred Years of Solitude in particular, he drew on his upbringing in the rural town of Aracataca, fictionalised as Macondo from his first book, the 1955 novella Leaf Storm, and on the history and heritage of his grandparents, with whom he lived as a young child. His grandfather, Col Nicolás Márquez Mejía, was a veteran of the thousand days’ war, fought between 1899 and 1902, and a committed liberal who was a significant influence on his grandson’s political thinking.

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Having started his career as a journalist, García Márquez spent much of his life living outside Colombia, in Paris, Barcelona and Mexico City, and also had the use of a mansion in Havana provided by Fidel Castro, with whom he enjoyed a “nuanced” friendship. But throughout, he maintained close links to – and another home in – Colombia. He was awarded the Nobel prize in literature in 1982.

The publication of Until August is being met with much excitement. The novelist Colum McCann, said: “What a joy it is to think that there are still things to discover in the world. I would walk 500 miles to get to a new Márquez book. It’s like discovering ice at the end of a long journey. Márquez is both beloved and necessary, a rare combination in the literary world. I remember my first experience of Márquez when I read his short story The Handsomest Drowned Man in the World. Suddenly things were just entirely new. He was cleaving open the language for me. Of course, every time you enter a Márquez book, there will be something new, even if you have read it four or five times. But to come upon a thing for the first time is a rare treat.”

The writer Pico Iyer also spoke of the impact that García Márquez had on writers and readers in a changing literary landscape. “I think part of the revolution García Márquez wrought was to expand our sense of realism and to help it to include those parts of the world less often familiar to the centre of the literary universe,” he told me. “The dreams of Kew are the facts of Kathmandu, as Kipling wrote, and García Márquez was one of the first, in our dawning global age, to see that the news from the far-off corners of the world might be arresting – even magical – to those in London or New York.” He added that García Márquez’s contribution to literature created a valuable space for later writers such as Salman Rushdie and Abraham Verghese, and that there was an argument for the Colombian writer being seen as the most influential Nobel laureate of recent decades.

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Posthumous publication is not uncommon, and can be controversial. Perhaps the instance closest to that of García Márquez is the decision by Vladimir Nabokov’s son Dmitri to publish his final work, The Original of Laura, more than 30 years after his father’s death. In the intervening period, it had languished in a Swiss bank vault as Dmitri weighed his father’s instructions to destroy any unpublished work against the knowledge that his mother had once intercepted Nabokov on his way to the incinerator with the manuscript of Lolita in his hands.

More recently, other examples have included works by David Foster Wallace, Roberto Bolaño and Stieg Larsson, the author of The Girl With the Dragon Tattoo trilogy, who died suddenly at the age of 50. After his death, his publishers hired the writers David Lagercrantz and Karin Smirnoff to write more novels in the Millennium series. The most notorious example is perhaps Harper Lee, whose unpublished novel Go Set a Watchman appeared in 2015, less than a year before her death, amid accusations that the author had been pressured into its release.

One critic of the decision to publish Until August posthumously is Miranda France, the consultant editor for Spain, Portugal and Latin America for the Times Literary Supplement. On an initial reading, she told me, she noticed that there was a comparative impoverishment in García Márquez’s customarily rich vocabulary, and said she found the experience poignant: “There are elements of what was there before, but I found that very sad, because I felt that the fuller narrative was missing.” The danger, she feels, is that “not only does it not really add, but it might actually slightly detract” from García Márquez’s otherwise “terrific” body of work.

When García Márquez’s sons were little, their father allowed them to help him destroy drafts of his works-in-progress that he no longer had any use for; he was, his editors and publishers attest, a perfectionist who monitored every change of punctuation and usage in his manuscripts as they made their way to his vast and enthusiastic readership. Now that readership will have the chance to judge whether his final piece of imagination should have seen the light of day.

• Until August by Gabriel Garcia Marquez (Penguin Books Ltd, £16.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.