I Think I Love You, By Allison Pearson

(Rex Features)

Petra is a bereaved, middle-aged divorcée who was once a skinny, virginal 13-year-old obsessed with David Cassidy. It's a passion she's almost forgotten, but one that has shaped her life. Like 30 million others in the early 1970s, Petra and her best friend Sharon once devoured The Essential David Cassidy magazine, convinced that their knowledge of the star's tastes would make them his wife and transport them from provincial Wales to California.

A quarter of a century later, Petra discovers that all these details were invented by Bill, an English graduate hired by the magazine. A modern Cyrano de Bergerac, he bashes out the "diary" entries and lies to his girlfriend that he's a glamorous rock-journalist. Bill's wit, cynicism and astringency about a man who "looks like a Jersey calf", and the deluded girls who adore him, are an essential counterpoint to Petra's story: if you're put off by the first chapter, the second, from Bill's point of view, will rapidly reassure you.

Petra looks back on her past with wonder, guilt and wry insights. Her passion for pop causes her to abandon her cello practice, lie to her mother and betray Sharon. Like the film Mean Girls, this is as much about the power-play between young girls as the gulf between innocence and experience. Essentially, it is a novel about the betrayal of the "deep self", what Proust called le moi profonde, to the trivial values of those we wish to please.

Petra, as her name suggests, is petrified into a state of passivity that leads to divorce and depression. It's not until she discovers how her joyless, frustrated German mother has suppressed a vital piece of information that she is able to pick up pieces of the past.

Allison Pearson's forte, as in her former incarnation as a columnist, is her warm, funny narrative voice. This reaches a climax half-way through when thousands of teenage girls descend on a disastrous farewell Cassidy concert in London. I don't think anyone can read the descriptions of Petra's and Bill's very different experience without tears of laughter.

After this, Petra's point of view switches, puzzlingly, from first to third person, and loses the ebullient quality that makes the first half so exceptional. The means by which the plot to its inevitable conclusion is joyously improbable, even though we know that Petra and Bill are destined to find true happiness: how could they not when Bill, pretending to be Cassidy, has prescribed his own ideal partner? Yet it's Petra's anguished relationship with her costive, cranky mother, Sharon and her own teenage self which give the novel genuine distinction.

I Think I Love You has been packaged as chick-lit, but like Pearson's first novel, I Don't Know How She Does It, it is far superior to the usual fare. There is a shapeliness and depth to the wit that reminded me of Nancy Mitford, and although this novel describes a much more modest social class, it is no less interesting or insightful about recent history. Pearson has given us a wise, elegant and heartfelt book about the splendours and illusions of first love – even if many of those who read it will only see the fun.

Amanda Craig's 'Hearts and Minds' is published by Abacus