Who among us can say we have never wondered what it would be like to enter the world of a favourite book? Sam Mills has certainly thought about it. She describes her first novel for adults, The Quiddity of Will Self (2012), as the ‘literary equivalent of Being John Malkovich’. It portrays a fictionalised version of Will Self, on whom other characters become so fixated that they undergo plastic surgery to look more like him. There are also sections written in a pastiche of Self’s style, with ample references to genitals and a lot of obscure words. It’s certainly original, but it will be a little baffling to anyone who isn’t a card-carrying member of the Will Self fan club.

In her new novel, The Watermark, Mills is still thinking about the interplay between fiction and reality. Jaime, a writer in his late twenties, has won a competition to interview the reclusive Augustus Fate – a favourite author of Rachel, whom Jaime met online and with whom he is now obsessed. However, when Jaime arrives at Fate’s remote cottage, he is given some ominously dark tea and slips into a coma, whereupon he joins Rachel, imprisoned as a character in Fate’s novel-in-progress, set in Oxford in 1861. In order to escape, they must navigate a network of other novels. As Jaime and Rachel move from Victorian Oxford to Manchester in the mid-2000s, interwar Russia and a near future dominated by robots, their budding romantic relationship grows, stalls and revives.

The Watermark contains five sections – one for each novel into which Jaime and Rachel are thrust – and Mills uses several tricks to differentiate between them. The perspective switches back and forth between Jaime and Rachel, each section is set in a markedly different period from the one it