The tale of how Audrey Niffenegger's first novel began life with a negligible print run and became a bestseller in the US, with rights sold in more than 15 countries and film rights bought by Brad Pitt and Jennifer Aniston, transforming the fortunes not only of the author but of her tiny, independent literary publisher, is even more heart-warming than the story that it tells. The Time Traveller's Wife has attracted comparisons with Alice Sebold's bestseller of last year, The Lovely Bones, partly in terms of its unforeseen commercial success but also presumably because, like Sebold's book, this story is a deliberate heartstring-tugger that depends on the reader's wil-ling suspension of disbelief in a ludicrous premise. Some critics might describe these novels as magical realist and trace their lineage to It's a Wonderful Life. Unkinder people might be inclined to use the word "mawkish".
In The Lovely Bones, the conceit was that the dead narrator was telling her story from heaven. The Time Traveller's Wife has two simultaneous narrators, Henry and Clare, and the fantasy element is that Henry suffers from "chrono-displacement disorder", a genetic flaw similar to epilepsy, which means that at moments of stress he disappears from the present and pitches up naked in his own past or future. This doesn't displace the present self of whatever year he is thrown into, so frequently he finds himself face to face with a younger or older double with whom he can communicate (we are even made coyly to understand that, as a teenager, he experiments with fellating himself) - which gives him plenty of opportunity to reflect on free will and predestination. This means that Henry first meets Clare, his wife, when she is six and he is 36, although technically he first meets her in the present when he is 28 and she is 20. If this seems confusing, it is - but Niffenegger's plotting is clearly undertaken with the utmost attention to detail, and each section, told in the present tense, is prefaced with enough information to orientate the reader: "Friday, September 23, 1977 (Henry is 36, Clare is 6)." This does require some effort until the bigger picture begins to build.
To write a novel in different first-person voices, laid out like monologues in a play script, is an ambitious choice of form, and for it to be successful depends on the writer's talent in making those voices distinct and memorable, as exemplified in Julian Barnes's novels Talking It Over and Love, Etc. Niffenegger hasn't quite scaled such heights; open The Time Traveller's Wife at a page without a section heading and it is hard to tell which "I" is speaking. Each is as artless as the other - paragraphs are padded out with details of what the characters eat or the clothes they wear, as if the author is over-anxious about rooting her fantasy idea in a convincing and recognisable reality: "All this time Gomez and Henry have been drinking beer and Charisse and I have been sipping wine and Gomez has been topping up our glasses and we have not been eating much but I do not realise how drunk we are until I almost miss sitting down on the chair Henry holds for me and Gomez almost sets his own hair on fire while lighting the candles." The would-be-witty conversations between the main characters are too painful to relate.
Halfway through, the story picks up as Henry meets Dr Kendrick, a geneticist who accepts the truth of Henry's condition and is prepared to analyse his DNA in search of both cause and cure. At the same time, Henry and Clare are trying to conceive and coping with the pain of serial miscarriages. Again, Niffenegger has spent a lot of time on research and her use of the language of genetics is impressive. But while the yoking together of scientific principle and fantasy is as old as science, there seems something distasteful about transferring the experiences of infertile couples afflicted with genetic disorders to the realm of time travel.
The Time Traveller's Wife is really a modern fairy tale - presumably the reason for its mass appeal - and will undoubtedly benefit from being unshackled from the page and transposed to the screen, where much of the background explanation can be rendered visually. Although it may not be a great novel, it is always heartening to see small publishers competing alongside the titans. The success of this kind of fantastical and sentimental story in the past couple of years tells us much about America's attitude towards reality.
Stephanie Merritt is deputy literary editor of the Observer