Esposito is effortlessly polite, but surprisingly at ease after being suddenly thrust into the spotlight by a book-and-film deal with several noughts. She is clearly no ingenue. Like Alvina, as pictured on the book's jacket, and soon to be blown up on billboards and the sides of buses, her blond hair is tucked coquettishly behind one ear. Which twin, I can't help wondering, is she going to be?
She grew up in Cheltenham, the only child of a French mother and a father whose work at GCHQ must never be mentioned.
"I always had my nose stuck in a book," she recalls, "because I didn't have anyone to play with at home. But all my friends had brothers and sisters, so I saw the relationship between sisters, and it was often nasty, violent and toxic."
This doesn't even begin to describe the hellish relationship she charts between blessed Beth and off-the-rails Alvie. "I thought," she says, "what would make me the most insanely jealous ever? What about if I had an identical twin sister who is more successful than me, more beautiful than me, richer than me, married to the man I was in love with."
And that is the premise of the novel, set in Beth's luxury villa on Sicily, complete with her good-looking husband, Ambrogio, her infant son, and her walk-in-wardrobe stuffed with designer labels. Alvie visits and seizes her chance in the pages of this racy, pacey Mafia-infused thriller to become her sister for a week. "Unity of time, place and action," she confirms, quoting a mantra from her academy training.
The plot owes a debt (freely acknowledged) to the global phenomenon that was Gone Girl, Gillian Flynn's 2012 page-turner, subsequently made into a film with Rosamund Pike as Amy Dunne, the woman who outsmarts men at their own game.
"I loved her," Esposito enthuses, before adding with a flash of steel, "but she's so humourless. She never cracks a smile."
Mad, therefore, is more a "Gone Girl-plus". (Two more volumes are in the offing, entitled Bad and Dangerous to Know.) Esposito has added a dollop of Bridget Jones to the mix: "It is kind of a black comedy - Bridget gone bad, 20 years on. She never had Tinder, for example."
Now we are getting on to another striking aspect of Mad - the sex. In Sicily, Alvie has little need for any online dating app as she works her way, hectically and graphically, through almost every man in her sister's circle, including her oh-so-gorgeous brother-in-law, who turns out to be not oh-so-desirable in bed.
"I do hope I win the [Literary Review's famed annual] Bad Sex Prize," giggles Esposito. "One scene is meant to be really bad sex."
And has her husband read her novel? "He might wait for the movie ... " she answers with a grin. "He's in finance, and he hasn't read a novel in the 11 years since I met him."
Not content merely to entertain, Esposito is keen to enter the gender war. "For me, Mad is a feminist novel for this generation. I know that the really strict, strident feminists will read it and think Alvie's a bad feminist because she is using her sexuality to manipulate men. But it is all about empowerment. She is the one driving the sports car in the high-speed chase. She is the one with the gun, shooting the bad boys. She is calling the one in control,
Some readers will inevitably wonder, with such a strongly-drawn character, if Esposito isn't also sharing part of herself. She shakes her head vigorously.
"Everyone has a shadow side, their subconscious desires, but this is, I promise you, just me letting my imagination run wild. In real life, I'm a good girl. Mad is complete escapism."
Mad, by Chloe Esposito (Michael Joseph, $37) is out on June 19.
