Even by its author's impressive standards, David Mitchell's Booker-longlisted sixth novel is recklessly ambitious. It is composed of six parts, each of which deals with a different chapter in the life of Holly Sykes, a teenage runaway who grows up to become a successful memoirist. Two sections – the first and last – are narrated by Holly herself; the others by figures who at various points come into contact with her. In the first section, set in 1984, 15-year-old Holly goes on the lam in Gravesend, Kent, after falling out with her parents and discovering that her boyfriend is cheating on her. In the final part, set some 60 years later, an elderly Holly hunkers down on Ireland's west coast as the world lurches towards environmental apocalypse and the global socio-economic order disintegrates.
In between, Mitchell ranges between styles and genres with his usual promiscuity. There's an embryonic Oxbridge novel that sees precocious, amoral Hugo Lamb describe his predatory life as a Cambridge undergraduate. (The link with Holly is that he seduces her at a Swiss ski resort.) Next, we skip forward to 2004, where we find Holly's partner, a foreign correspondent, ignoring the needs of his family while he fixates on the horrors he's just witnessed in Iraq. In the near future, there's an elaborate (and extremely funny) literary satire that centres on Crispin Hershey, a former "wild child of British literature" whose career is in freefall. (He befriends Holly on the literary festival circuit.) The fifth section, meanwhile, is wholly different from all the others; it concerns (yes, really) a centuries-long battle between two tribes of immortal beings.
Those acquainted with Mitchell's previous work will know that, in his fictional universe, pretty much anything can happen. Still, the genre-bending he attempts in The Bone Clocks is startling. Over the first four sections (which, for the most part, are realist narratives), the reader becomes aware that some decidedly weird stuff is going on in the background. Life as it is ordinarily lived can, seemingly at random, be cosmically interfered with. At such moments, the fabric of the physical world parts like a curtain, revealing figures from a shadowy alternative realm.
The agents of this tampering are "atemporals" : ostensibly normal beings who live among their human counterparts, carrying on their dark work largely undetected. The atemporal realm is itself split between the Horologists, who achieve immortality through reincarnation, and the Anchorites, who fuel their longevity by ritually slaughtering children. Basically, the Horologists are good guys – blameless recyclers who use their powers to do good. The Anchorites, meanwhile, are selfish plunderers who look out only for themselves.
The two tribes' contrasting methods of life-prolongation are significant, for they connect the novel's fantasy subplot with its author's real-world ethical and environmental preoccupations. Throughout his career, Mitchell has been interested in the relationship between personal and planetary ethics; in how individual self-interest can be reconciled with the larger imperative of human survival. The tribes in The Bone Clocks embody different approaches to such questions.
In the Crispin Hershey section, a literary agent tells him that "a book can't be half-fantasy any more than a woman can be half-pregnant". And indeed, there are many reasons why a novel like The Bone Clocks shouldn't work. Yet what's surprising – and a testament to Mitchell's singular abilities – is that for the most part it does. It helps that Mitchell keeps a tight lid on the fantasy element while the more realist sections are under way; the activities of the atemporals are glimpsed only in fragments, which pique the reader's curiosity but don't distract from the main story. Because the two elements don't bleed too much into each other, The Bone Clocks doesn't end up feeling like a clumsy halfway house.
And along the way, there's much to relish. Mitchell's plotting is as intricate as ever, and he indulges in many familiar tricks. Themes, characters and images recur in different configurations, as in a complex musical work; characters from earlier Mitchell books make guest appearances; there are sly references to Mitchell's literary reputation, as well as to the works of other writers. (One of Crispin Hershey's early novels, for example, is called Desiccated Embryos. Geddit?) It's all a bit mad, and in some ways quite silly, and, no doubt, questions will be asked about what The Bone Clocks finally adds up to, whether, in fact, it can be classed as "serious" literature at all. (For this reason, I doubt it will win the Booker.) But such questions largely miss the point. Mitchell is a writer who will always do his own thing, and the question to ask about his work isn't how profound it is, or what category it belongs to, but how much fun it is to read. And on that measure, The Bone Clocks scores highly.
The Bone Clocks is published by Sceptre (£20). Click here to buy it for £15.49 with free UK p&p
• This article was amended on 8 October 2014 to correct the character Hugo Lamb's name. The original mistakenly called him Alex.
