The giants of bestselling Spanish-language fiction – the chroniclers of deluded chivalry, intellectual and psychological labyrinths and the odd dynasty condemned to a solitudinous century – enjoy a formidable worldwide reputation. Miguel de Cervantes, Jorge Luis Borges or Gabriel García Márquez are known well beyond their homelands.

Not so Corín Tellado. This remarkable and unassuming Asturian author, who died in 2009, produced more than 4,000 works during a six-decade career. If she has an equivalent in the English-speaking world, it is Barbara Cartland rather than George Eliot. But her escapist tales of love and loss, suffering and redemption, have sold more than 400m copies – and a great deal more than that if the millions of pirated Latin American editions are counted. In 1962, Unesco declared her the most-read Spanish author alongside Cervantes.

Now English-speaking readers are about to get their turn. Having been embraced by ordinary Spaniards and Latin Americans and derided by critics, Tellado is finally vaulting the linguistic divide with the publication of the first professional English translation of one of her novels.

Thursdays with Leila (Los Jueves de Leila), which comes out this month, is a typical romance or novela rosa. Orphaned but spirited heroine? Tick. Dangerously sexual male character with eyes as “grey and steely, as cold as knife”? Tick. Outrageous reversals of fortune? Well, obviously. Like most of Tellado’s output, the book follows a well-worn plot pattern. That, however, does not make it worthless. Just ask Mario Vargas Llosa, who has supplied the prologue to the translation.

“[Tellado] was, in all likelihood, the most significant sociocultural phenomenon in the Spanish language since the Golden Age,” writes the Peruvian-born Nobel laureate. “What might ostensibly appear to be heresy – and from a qualitative perspective it is – ceases to be so if we begin to view things in quantitative terms. Borges, García Márquez, Ortega y Gasset, any of the most original thinkers and writers in my language that you might care to mention, none of them have reached as many readers or had so great an influence on the way in which people feel, speak, love, hate, understand life and human relations, than María del Socorro Tellado López, Socorrín to her friends.”

Corin Tellado in 2006. Photograph: Quim Llenas/Cover/Getty Images

Vargas Llosa, who became aware of Tellado’s work in the early 1960s when his niece arrived from Lima to visit him in Paris carrying a suitcase stuffed with Tellado’s books, met the author 20 years later when he interviewed her for a Peruvian TV programme.

The Tellado he found was a frugal, shy and modest woman in her 50s, “completely unaware of the tremendous popularity she enjoyed in the media and popular imagination of over 20 Spanish-speaking countries”.

The translator of Los Jueves con Leila stumbled across Tellado in more prosaic fashion. Duncan Wheeler, associate professor of Spanish studies at the University of Leeds, was researching the cultural politics of Spain’s post-Franco transition to democracy when he noticed that her readers had been ignominiously lumped in with fans of Julio Iglesias and his ilk.

After devouring 50 of her books bought for a euro each at Madrid’s El Rastro flea market four years ago, he began to look beyond the comparisons with Cartland and consider Tellado as a chronicler of Spanish society.

“I think people are very snotty about Corín Tellado in Spain, so I think it’s a fair enough comparison: the books are what they are – they’re page-turners,” he says.

“They do work on that level but you can tell from the sexual morals and the language used – as in the complexity of the vocabulary – when they first came out. One of the cornerstones of my research is that the history of Spain has been written too much through the politics. Obviously the dictator dying in 1975 is a huge thing – and you can never deny that.”

None the less, says Wheeler, the books offer a valuable overview of an evolving Spain. Not only do they reflect the changing status of women as the tourism boom allowed them to leave home to work in hotels and other service industries, they also depict the country’s nascent celebrity culture and its fascination with all things American.

Wheeler, who describes Thursdays with Leila as similar to the film Indecent Proposal – “but 30 years earlier” – believes Tellado set it in the US rather than Spain not because its subject matter might have attracted the attention of Franco’s censors but because it better suited the appetites of her readers.

“This was the period of the explosion of Hola!, of celebrity culture and lots of people like John Wayne were coming to Spain. There was a fascination with American culture and I think it’s about selling a lifestyle, with detailed descriptions of living rooms or of cars.”

Tellado’s daughter, Begoña Tellado Egusquizaga, is delighted at the prospect of English readers becoming acquainted with a woman who “lived by and for her work”. Her mother’s gifts, she says, went beyond stamina and skill.

“She was just able to reach people in a really direct way and the public took to her. She could write a novel in two days – they were ‘simple’ novels but they must have been hard to write. They were real-life stories and people identified with them.”

Wheeler hopes the translation will provide people with a new perspective on recent history.

“I think it will offer them an image of Spain and of Spain’s transition to democracy that is neither the sun-sea-sex-and-sangría image that’s been sold very simplistically,” he says. “Neither is it the picture we’ve had of high culture taking on the censor. It gives a snapshot of how Spain was both different but not so different to the UK and other European countries in the 1960s.”

And besides, he adds, “it’s a good page-turner”.