With The Real Lolita, Sarah Weinman might be said to have invented a completely new genre: true-crime literary criticism, which is not to be confused with truly criminal literary criticism, which, of course, is most literary criticism. The Real Lolita is, by any measure, a unique and very peculiar book.

The sad real-life story of Sally Horner, as recounted by Weinman, goes like this. Born in 1937, Florence ‘Sally’ Horner lived with her mother at 944 Linden Street, between Ninth and Tenth Streets in Camden, New Jersey. Her father killed himself when she was six. In March 1948, aged eleven, on her way home from Northeast School, where she was a fifth-grade honour pupil and president of the Junior Red Cross Club, she stole a five-cent notebook from the Camden Woolworth’s on Broadway and Federal. On the way out of the store, she was caught by a man who told her he was an FBI agent. He agreed to let her go if she promised to report to him occasionally.

A few months later, in June 1948, the man caught up with Sally on her way home from school. He told her that she was required to accompany him to Atlantic City. He then telephoned Sally’s mother, Ella, pretending to be the father of a friend of Sally, inviting the girl to join him and his family on holiday. On 14 June, Ella dropped Sally at the Camden bus depot. Almost two years later, in March 1950, after an unsuccessful police hunt, Sally telephoned her family from San Jose, California, asking them to rescue her. Her abductor, a man calling himself Frank La Salle, but also known by a number of aliases, pleaded guilty to a charge of kidnapping. He had already served time for the rape of five girls. La Salle – who insisted in court that Sally was his daughter – died in prison. Tragically, Sally died in a car crash, aged just fifteen, in August 1952.

Weinman is at her absolute best when playing detective and piecing together this tragic tale in all its sordid detail. ‘I tell crime stories for a living,’ she writes. ‘They ignite within me the twinned sense of obsession and compulsion. If these feelings persist, I know the story is mine to tell.’ She makes this one hers: the book contains twists and near misses and bit-part players, everything you might expect from a true-crime story, startlingly and simply told. In July 1948, for example, just a month after the abduction, a family named the Pfeffers broke down in their car on Route 40, just outside Atlantic City, and were picked up by La Salle with Sally, who happened to be driving past. The Pfeffers later recalled that Sally referred to La Salle as ‘Daddy’, and that he invited nine-year-old Barbara Pfeffer to come and stay with him and Sally. As Weinman puts it, blankly, ‘The family did not take them up on the invite.’

So far so bad – and so so good. The problems arise when it comes to Nabokov. The resemblances between the Sally Horner story and Nabokov’s Lolita are well known to scholars, thanks to the work of Alexander Dolinin, whose article ‘Whatever Happened to Sally Horner? A Real Life Source of Nabokov’s Lolita’ – which is acknowledged as a source by Weinman – appeared in the TLS in 2005. Dolinin’s article is exactly the sort of thing one might expect to find in the TLS. At times, Weinman’s book is more like something one might expect to find extracted in the Reader’s Digest. Recounting Sally’s story, Weinman is the very model of intelligence and restraint, but when it comes to her recounting of the making of the ‘novel that scandalized the world’, the prose loosens up and loses its focus: ‘By exploring the life of Sally Horner, I reveal the truth behind the curtain of fiction. What Humbert Humbert did to Dolores Haze is, in fact, what Frank La Salle did to Sally Horner in 1948.’

Nonetheless, the necessary points are carefully made and carefully reiterated, and the correspondences noted and remarked upon: the middle-aged sexual predator, the young girl, the widowed mother, the two years of moving around America. As Weinman rightly points out, Nabokov began writing Lolita long before he’d heard about the Sally Horner case: ‘There is no question Lolita would have existed without Sally Horner because Nabokov spent over twenty years dwelling on the theme … But the narrative was also strengthened and sharpened by the inclusion of her story.’ The literal inclusion, in fact: towards the end of Nabokov’s novel, Humbert Humbert asks himself, ‘Had I done to Dolly, perhaps, what Frank Lasalle, fifty-year-old mechanic, had done to eleven-year-old Sally Horner?’ Perhaps? Indeed.

In the end, The Real Lolita succeeds, like so much true-crime writing, and indeed like so much literary criticism, because its author shares just a little of the disturbing and obsessive compulsions of some of the persons discussed. ‘Even after chasing down court documents,’ writes Weinman, ‘talking to family members, visiting some of the places she had lived – and some of the places where La Salle took her – and writing the piece, I knew I wasn’t finished with Sally Horner. Or, more accurately, she was not finished with me.’ The value of The Real Lolita lies precisely in the real. ‘It is strange,’ wrote Nabokov in his study of Gogol, ‘the morbid inclination we have to derive satisfaction from the fact (generally false and always irrelevant) that a work of art is traceable to a “true story.”’ Oddly, in this case, it’s not the true story that is irrelevant: it’s Nabokov.