The scandal surrounding John Ruskin, his wife Effie, and John Everett Millais still fascinates a century and a half after the events. What makes it famous is that it wasn't a sex scandal but a non-sex scandal.

The circumstances in which Effie left her husband for the pre-Raphaelite artist have generated at least half a dozen books as well as an opera, a silent film and assorted plays. One of the plays, The Countess, was at the centre of a just-resolved copyright dispute between its author, Gregory Murphy, and the actor Emma Thompson. Thompson has written the screenplay for Effie, a big-screen telling of the story starring her husband Greg Wise as Ruskin, Dakota Fanning as Effie and Tom Sturridge as Millais; the film is scheduled for release in May.

The outline is familiar. In 1848 the 29-year-old Ruskin – two volumes of the influential Modern Painters to his name and at work on The Seven Lamps of Architecture – married Euphemia Gray, the beautiful 19-year-old daughter of family friends. After six increasingly unhappy years, Effie fell in love with her husband's protege Millais and set about having the marriage annulled.

What reverberated then and now was that the reason given for ending the union was non-consummation. But what really snagged in the public consciousness was Ruskin's explanation of why he didn't fulfil his marital duties: "It may be thought strange that I could abstain from a woman who to most people was so attractive. But though her face was beautiful, her person was not formed to excite passion. On the contrary, there were certain circumstances in her person which completely checked it."

Those "certain circumstances" have been the cause of much salacious speculation. The reasons mooted range from his aversion to children, his religious scruples, a wish to preserve Effie's beauty and to keep her from exhaustion so they could go Alpine walking, to a revulsion with body odour and menstruation. Effie herself was the inadvertent source of the most famous of explanations: Ruskin, she said, "had imagined women were quite different to what he saw I was, and that the reason he did not make me his Wife was because he was disgusted with my person the first evening". From this emerged the canard that Ruskin, used only to the smoothness of classical statues of the nude, was repulsed by the wedding-night revelation that Effie had pubic hair. It may not rival Cleopatra's nose, but poor Effie has gone down as the possessor of the most famous genital coiffure in history.

The truth about the wedding night and marriage can never be fully known, but a new book, Marriage of Inconvenience by Robert Brownell, is about to revise perceptions of the whole sad episode. Much of the correspondence between the parties was subsequently edited or destroyed by Effie's relatives to protect her reputation as the injured party. Brownell, though, has subjected the surviving letters to a forensic reading and has drawn conclusions that are at odds with the established story.

Ruskin and Effie had known each other since she was a child. Both came from Perth families, and the Grays moved into the old Ruskin family home after John's father, a successful wine merchant, relocated to London for business. Effie would stay with the Ruskins during school holidays and John wrote his fairytale The King of the Golden River for her.

Ruskin was an only child, doted on by his parents and afflicted by both his mother's intense religiosity and ill-health. He may well have had tuberculosis, although his father ascribed his ailment to "over Study" – not impossible since, at the age of 12, he had written a 2,212-line poem about a family tour of the Lake District. Whatever the reasons, the young Ruskin was reserved, unsure of the opposite sex, a poor horseman and with hesitant social skills. Poignantly he wrote of himself: "If I had been a woman, I never should have loved the kind of person that I am."

Effie, on the other hand, was lively, flirtatious, clever but under-educated. When her mother heard intimations that Ruskin had begun to see her in a non-sisterly light, Effie responded: "that John and I should love each other – wasn't it good, I could not help laughing". When he did declare himself, his letters were indeed laughable – the prose stylist turned gusher: "You saucy – wicked – witching – malicious – merciless mischief-loving – torturing – martyrising … mountain nymph that you are." Nothing of matching intensity from her has survived.

Ruskin's first proposal was not accepted. Effie had an acknowledged "understanding" with a soldier about to go to India and an interest in at least six other young men. Mrs Gaskell, who had attended the same school – though earlier – recounted gossip she heard of Effie collecting admirers as a hobby. What changed her mind, Brownell says, was her father's financial situation. Mr Gray was an inveterate speculator and his investment in railway shares threatened to bankrupt him. Either Effie herself, or more likely her father, saw marriage into the wealthy Ruskin family as the only way to maintain the Grays' creditworthiness. So the Grays brought forward the wedding date to forestall the bailiffs; Effie married with no dowry, but instead had £10,000 settled on her by Mr Ruskin; and the ceremony took place in Scotland with none of John's family present. The Grays had been saved, but Ruskin had been duped.

It was the realisation of this duplicity that was, Brownell argues, the reason for the non-consummation of the marriage. Before the wedding Ruskin had written to his bride-to-be with coy but panting excitement: "That little undress bit! Ah – my sweet Lady – What naughty thoughts had I …" but he also had viewed her with realism ("she is unfitted to be my wife unless she also loved me exceedingly"). Despite the fact that they shared a bed, the knowledge that he had unwittingly entered a marriage with love on one side only meant that his naughty thoughts never became deeds: he was too scrupulous to have sex without reciprocity. They agreed instead to wait six years, when Effie would be 25, to give themselves time to fall properly in love before broaching the subject again.

Love was to prove a vain hope; the most they ever managed was fondness, and that began to erode soon enough. There was an added overlay of friction caused by Effie's resentment of John's parents, who paid for the couple's comfortable lifestyle and kept a close watch on them in return. Effie was thought to need supervision: during two long stays in Venice in 1849 and 1851, while Ruskin was researching The Stones of Venice, he left her pretty much to her own devices in a city crawling with Austrian army officers after their recent successful siege.

Effie had no trouble attracting admirers. She wrote to her brother: "Venice is so tempting just now at night that it is hardly possible not to be imprudent." Her imprudence led to her encouraging – intentionally or not – a number of soldiers. The results escalated from arguments between them over her dance card (she was a committed polka dancer) to a duel in which one admirer was killed. At least two slighted others came openly to express their hatred for her, and things were exacerbated when some of her jewellery was stolen and suspicion fell on another soldier-admirer. According to gossip, perhaps the diamonds weren't in fact stolen but given.

Effie now had a reputation that followed her to London to the extent that the unmartial Ruskin himself was twice challenged to a duel by friends of the jewel-thief officer. It was at this point, Brownell says, that Ruskin rather than Effie actively started to look for a way out. His cat's-paw presented itself in the shape of Millais. Ruskin had defended the painter against critical attacks, and soon Effie was modelling for his appositely titled picture The Order of Release. She was willing – as she wrote to her mother: "Millais is so extremely handsome, besides his talents, that you may fancy how he is run after."

In the summer of 1853 Ruskin invited Millais to join them on a Scottish holiday to paint his portrait. He rented a cottage and left his wife and the painter alone together as much as possible, all the while keeping an "evidential diary". Ruskin's aim, says Brownell, was not divorce (it was so difficult, demeaning and expensive that there were on average only four divorces a year in England at the time) but annulment, which allowed for the dissolution of a marriage on the grounds of, among other things, bigamy, kidnap, incest or non-consummation due to incurable impotence or mental/physical inaptitude.

Ruskin was willing to take the stigma of non-consummation on himself because he wouldn't be medically examined and nor were annulments usually reported in the press. If Effie's father had helped dupe Ruskin into the marriage he was in turn duped into ending it. Ruskin, says Brownell, used the threat of divorce and the ensuing scandal to pressurise Mr Gray into persuading Effie to instigate annulment proceedings instead. The ruse worked. Two doctors attested to Effie's virginity, Ruskin himself was out of the country at the time, and in 1854 the marriage was officially ended.

In fact Effie emerged from the whole business rather better than Ruskin. Her friends – and his enemies – used the non-consummation clause as a means to malign him, while he remained stoically tight-lipped. She also later ended any hopes he had of finding happiness with another young girl, Rose La Touche, by warning her parents about him. Her own marriage to Millais, though, was a success, and consummated with such relish by him that they had eight children and she was forced to write to him imploringly: "Basta!"

Ruskin himself did find love of sorts, however, with his books. Without the distraction of a wife he went on to become England's greatest critic and social thinker of the 19th century. Neither Ruskin nor Effie, however, fully managed to live down those "certain circumstances", however. Until now.

• This article was amended on 1 April 2013. The original said Mrs Gaskell was at school with Effie. She did attend the same school, but much earlier.