Bloomsbury £16.99 pp305

Jessamy Harrison is a precocious and troubled eight-year-old. The daughter of a Nigerian mother and an English father, she lives in suburban Kent, an only child, unpopular at school, and given to tantrums. She spends hours alone in her bedroom composing haikus, and sometimes takes refuge in the airing cupboard, which gives her a sense of security.

During a trip to Nigeria, she encounters a mysterious small girl called TillyTilly, who seems to be the friend she has always longed to have. TillyTilly subsequently turns up in England, a provocative companion who appears to have supernatural powers and who encourages Jess to misbehave. Jess’s tantrums become more frequent and violent, and she finds herself increasingly sucked into a parallel world where time and substance are fluid. By relating the story from the point of view of an eight-year-old, Helen Oyeyemi is able to spin out the central mystery of TillyTilly’s true identity. Is she a real girl or an imaginary friend? A lost twin or a dangerous alter ego? A sad ghost wanting to return to the real world or a sinister spirit who wants to steal Jess’s life? Is a psychiatrist the answer to Jess’s behavioural problems or should her parents commission an ibeji carving — something that, according to Nigerian tradition, they should have done at her birth?

Oyeyemi’s ambitious first novel (written while she was studying for her A-levels) succeeds best when it deals with Jess’s dual inheritance and the tensions experienced by a “half-and-half child”. The author plays numerous sophisticated games with notions of twinship and identity and, perhaps because at 20 she is not far removed from it, convincingly re-creates the not altogether attractive world of small girls. A more practised writer might have resisted the temptation to slip briefly into the consciousnesses of other characters, which feels rather like a narrative cheat, but the principal flaw in this otherwise impressive novel is the amount of time devoted to Jess’s other world. Listening to other people’s dreams can become tedious, and reading about them runs the same risk. Used more sparingly, this device would be fine, but Jess’s excursions into fantasy (if that’s what it is) are both lengthy and repetitive. For these reasons, The Icarus Girl is not quite the literary marvel that advance publicity has suggested. It is nevertheless a highly auspicious fictional debut.

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