The feeling of deja vu is appropriate. Oliver's first book, the engaging Before I Fall, draws heavily on that hymn to unoriginality, Groundhog Day. In Oliver's retelling, a young woman, Sam Kingston, relives the day of her death, learning new details about her existence each time, but ending up in the same car crash over and over again.

Delirium borrows from other sources and for different reasons. The story is as old as storytelling itself: two young, star-crossed lovers meet, fall in love and, well, to reveal more would spoil the ending. The central pairing of Lena and Alex are as intensely aware of the obstacles to their love as to that love itself. In this, they resound to echoes of Tristan and Isolde and more explicitly Romeo and Juliet: Oliver slips the play into Lena's hand in much the same way that Stephenie Meyer gave it to Bella Swan in Twilight: New Dawn.

The resemblance to Meyer is obvious, but striking. Like Bella and Edward, Lena and Alex are thwarted not by warring families or rival factions but by a genre. In Twilight, it's horror: the inconvenient fact that Edward Cullen is undead. In Delirium, Lena and Alex are scuppered because they live in George Orwell's 1984. Or perhaps it's Brave New World, Fahrenheit 451, A Clockwork Orange or Margaret Atwood's The Handmaid's Tale.

Here's the opening which explains Oliver's own high concept: 'It has been sixty-four years since the president and the Consortium identified love as a disease, and forty-three since the scientists perfected a cure.'

This is America (Portland, Oregon, to be precise) - but not quite as we know it. Having decided amor deliria nervosa is to blame for almost every mental, physical and emotional disturbance imaginable, from heart disease to bipolar disorder, romantic love is made illegal, and then defined as the most contagious virus in need of immediate eradication. 'The deadliest of deadly things: it kills you when you have it and when you don't.'

After each citizen celebrates their 18th birthday, they are assessed and undergo a procedure which removes their desire to desire. Judging from older Portlanders, the procedure doesn't simply remove a yearning to smooch; it lays waste to all tenderness, compassion and basic human sympathy.

Oliver is rather vague when describing this cure for love: one assumes a form of lobotomy, which leaves three small but visible puncture marks on the neck. Unlike dystopians such as Orwell, Huxley, Burgess, Bradbury and Atwood, she is not especially interested in describing the totalitarian mechanics of her loveless new world. Oliver's focus is on the personal: how Lena feels, or to start with doesn't. At the outset, she can't wait to have the crusts cut off her emotions: 'I don't like to think I am walking around with the disease running through my blood. Sometimes I swear I can feel it writhing around my veins like something spoiled, like sour milk.'

The most pressing explanation of Lena's initial submissiveness lies close to home. Her mother died for love: for her husband but also for Lena herself. Having refused to surrender her right to feel, she was tortured by the state, subjected to countless 'procedures' and eventually committed suicide rather than give up her humanity. Of course, this is not the story Lena has been told. And yet something in her memory strains towards the truth. These are her mother's final words: 'I love you. Remember. They cannot take it.'

We suspect that Lena will be made into a rebel, but she wasn't actually born one. As with Bella, Lena expends entire pages insisting that she is nothing special - to such an extent that it becomes really rather remarkable. 'I'm not ugly, but I'm not pretty either,' she says, singing what is her signature tune. 'Everything is in-between.' Ironically, the one factor that makes Lena stand out from the crowd is that she is only 1.6-metres tall.

Lena's hero-in-waiting is a rebel of the most handsome, but polite variety. Alex is not so much like his namesake in A Clockwork Orange as his own regularly praised hair: wild, but coiffured and somewhat reined in.

What truly holds the interest is Lena. Her gradual disillusion and rebirth is emotionally believable and imaginatively engrossing. It is Lena who drives the plot: will she escape; will she choose her family or Alex; will she discover the truth about her mother?

But Lena also carries the thematic weight of Delirium. She is an allegory for that awkward age - the transition from childhood to adulthood, and the realisation of a private self in an often disapproving adult world. The confusion Lena feels when she gets her first kiss (beautifully described by Oliver) is all too convincing: 'I wish it would stop. I want to go on forever.'

Buried in here somewhere is a slightly woolly critique of contemporary America: isolationism vs intervention; fear and safety vs expansion and risk. Yet Oliver is on surest ground when she writes about the dangerous thrill, both beautiful and transgressive, of sexual and romantic feeling. In Delirium, this is no small potatoes, but an entire philosophy of what it means to be human. Lena recalls the warning that love disables your ability to reason clearly. 'But it does not tell you this: that love will turn the whole world into something greater than itself.'

This could be trite in the hands of a lesser writer. Oliver triumphs because sentiment always mixes with a lack of sentimentality: happiness really is accompanied by unhappiness, pleasure by pain and self-realisation by sacrifice.