Already a runaway bestseller in its native France, Based on a True Story is unlike anything else you are likely to read this year. A taut, ferocious psychological thriller, it combines the masterful plotting of The Talented Mr Ripley with the manipulative malice of Notes on a Scandal. Inevitably, it will invite comparisons to Gone Girl, but Delphine de Vigan goes much further than Gillian Flynn in exploring the complex, fractious relationship between fact and fiction.

It will definitely spark a similar word-of-mouth frenzy, with people asking each other two questions: what did you think of that ending, and, is it actually based on a true story? Certainly, there are some signs that point to yes. The narrator is also called Delphine and works as a writer in Paris. Overwhelmed by the huge success of her latest book, exhausted and unable to begin writing the next one, Delphine meets L. Outwardly, with her smooth hair and perfectly filed nails, L. is the sort of woman who has always intimidated and impressed Delphine. She also seems to possess an uncanny knack for saying the right thing and turning up just when Delphine needs someone. So far, so very Single White Female. But there is something darker and more insidious at play here. L., who is a ghostwriter by trade, wants Delphine to start writing non-fiction, warning her that readers demand ‘authenticity’ and won’t settle for anything less. Delphine resists, arguing that writing her last book, based on her mother’s bipolar disorder, has left her emotionally drained. But L. is not the sort of woman to take no for an answer and, in the face of Delphine’s mounting inability to write, starts to answer her emails for her, and slowly but surely take over her life.

Clever, compulsive and disquieting, this is a challenging exploration of female friendships as well as a journey inside the mind of a writer. When asked in an interview if L. ever existed, de Vigan replied, ‘Yes, in one form or another’. Readers are left to meditate on what the ‘truth’ of fiction, or indeed autobiography, may actually be.

Hilary Simmons