Meet Ada, the anguished young narrator of 26-year-old Albertine Clarke’s radically strange and engrossing debut novel. Adrift in London, Ada occupies herself by swimming in her apartment’s basement pool and generally hiding from the world until she finds herself on the verge of a tumultuous mental collapse. If you’re allergic to the kind of novel in which characters exchange lines such as “I’m not real”, “Neither am I”, then it’s a case of diminishing returns. Otherwise, the book bears rich rewards.

The title refers to Ada’s father, an IT technician who is kicked out by Ada’s mother when he becomes obsessed with the gym – and much of the book explores how we create ourselves and others. Ada grows up surrounded by the marshy countryside near Norwich and early on experiences episodes of dissociation and ontological insecurity, including auditory and visual hallucinations. She imagines a voice on the radio saying her parents are getting divorced. The voice is “like a door swung open inside her head. Through it she could see a black tunnel, like a mine shaft, stretching down inside her.”

This voice follows her into adult life, and her listless days by the pool. It’s here she meets an older man named Atticus, a writer with an American accent. His male gaze is an affront to her: “She was not used to being looked at. It was as if curtains had been drawn back to reveal a secret audience she hadn’t realised she’d been performing for.” Despite this, they fall for each other, but stop short of intimacy when Atticus flies back to California. In his absence, Ada becomes convinced “they were connected. Atticus had her memories.”

We then follow Ada as her sense of a coherent identity slowly disintegrates while attempting to do normal things such as meeting her troubled cousin, or picking up a young admirer named Patrick, who declares his love unaware of the mental depths in which she’s drowning: “All she could think about was Atticus. She felt that she was becoming two people, her vision bisecting into two translucent images laid across each other.”

Further episodes of transference occur in the book’s most striking section when Ada goes on a disastrous holiday to Naxos with her estranged mother, during which her extreme behaviour escalates. She wonders if a mole on her shoulder is “some kind of surveillance device” and snips it off (“it seemed like too much blood”). While there’s an echo of Deborah Levy’s Hot Milk here, the book’s real antecedent is surely The Bell Jar. When Ada’s predictable breakdown arrives, she believes she’s somewhere else entirely, in this case a care facility with excellent room service and a pool. Here she hallucinates a room with a jungle in it, where she meets a mysterious Polish man named Darrius. It’s Darrius who confesses that he’s not real, only for Ada to shoot the same self-perception back at him.

Ada’s efforts to control her own mental environment are what give her a measure of agency and send her on the road to recovery. Like so much else, Darrius was merely a facet of her intensely imagined phantasmagoria: “She had made him and demolished him with the sadism of a child.” Back in London she has a brief and tentative rapprochement with her father. When the perhaps chimerical Atticus returns, she has to choose between him and the more dependably real Patrick.

Written with great clarity and imaginative resourcefulness, The Body Builders feels like a literary take on Polanski’s Repulsion coupled with Michel Gondry’s Eternal Sunshine of the Spotless Mind. While flirting with the subgenres of both body horror and the pejoratively named sad girl lit, the novel is finally a forceful performance from a promising new talent.