David Mitchell's new novel The Bone Clocks starts with a teenage girl listening to LPs in her bedroom in the 1980s and ends with two groups of super-humans battling it out in another dimension.

This is what Mitchell does: he puts the domestic and fantastic together; he hints at the connections between them; he starts a sentence with the normal and ends it with the extraordinary or the other way round; and he constantly demonstrates his greatest skill, which is the literary hand-brake turn - a sudden change of direction and speed that is unexpected and daring and exhilarating. He did it gloriously and inventively in Cloud Atlas and he does it again in The Bone Clocks.

So why is The Bone Clocks not a completely satisfying novel? Partly, it is because the novel repeats the structure and explores many of the same ideas as Cloud Atlas and, to that extent, it is familiar in the way that Cloud Atlas was surprising. It is also partly because The Bone Clocks is, like Cloud Atlas, a novel told from a number of perspectives and the danger of a novel with that kind of structure is that some of the perspectives will be less interesting than others. In Cloud Atlas, they were all compelling; in The Bone Clocks, less so.

The most satisfying stories in the new book are the first two: the story of Holly Sykes, a teenager who runs away from home, and of Hugo Lamb, a student and con man whose life unravels while on a skiing holiday with friends. Both are written with Mitchell's great feel for mood and character. In the case of Holly, it is the 1980s that are summoned up and anyone who was there will hear and feel it on the pages. In the case of Hugo, we are presented with a young man who commits despicable acts but is nevertheless likeable and, in its more scabrous and violent detail, his story has the swagger and uncomfortable joy of Irvine Welsh at his best.

These two early stories, of Hugo and Holly, also demonstrate some of Mitchell's greatest skills, including the ability to suddenly take off from the conventions of traditional narrative. The two most astonishing sequences happen in Holly's story, first when she experiences a daymare that gives one of the first hints of the super-beings that will become the heroes and villains of the story, and secondly, when we travel back through Holly's memories that "billow ... like windy sheets on a washing line". It is the most exciting, moving and imaginative sequence in the novel.

It is only when Mitchell explains the mysteries and, after all the hand-brake turns, hands the reader a road map, that the novel becomes less satisfying. Essentially, Holly has become involved in a war between two groups of superhumans: one that has achieved immortality with an ability to jump into new bodies and another that has achieved the same thing by sucking the life force out of others. But the section of the novel that focuses on their story lacks the invention and pace of the other chapters. It is also hampered by some of the conventions of a Hollywood science-fiction epic and, in the villains, the dialogue of the B-movie.

Unengaging as this section is, it cannot completely undermine The Bone Clocks because, at its best, it is ambitious, elegant and thoughtful. Particularly good are Mitchell's contemplations on ageing and mortality. The title of the novel is itself a reference to ageing (we are made of bones that will one day let us down; we are clocks ticking towards death) but Mitchell tackles entropy, ageing and death from every angle. His human characters can sense their own frailty ("DNA frays like wool and down we tumble") but the great message of The Bone Clocks, its warning if there is one, is that it is not just humans that age, it is everything. The last chapter, which features Holly as an old woman living in Ireland, is about the ageing and death not just of humans, but of the planet too: flesh and bone die, says Mitchell, but so too does rock and stone.