Mario Vargas Llosa's The Bad Girl is the story of a lifelong obsession. We begin in Lima, in 1950. Ricardo, a nice middle-class boy, falls for the exotic charms of Lily, whose audacious dancing and mischievous spirit capture his pubescent heart. Throughout his existence - and the novel - she flits in and out of his life in ever increasing moral and physical decrepitude, each time wounding him more deeply.

The action is a series of peaks and troughs, consisting of periods of frenzied activity, mostly sexual, alternating with long stretches of inactivity.

Since the excitement coincides with the appearances of Lily, the Bad Girl herself, this may have been a conscious device to contrast the thrill of her presence with the emptiness created in Ricardo's life by her absence. Sadly, it is not enough to sustain the reader who, faced with another description of life as a translator for Unesco, finds the attention wandering. That is not to say the writing isn't gripping. The sights, sounds and flavours of the boy's life are richly recounted in elegant prose, and it is this, not the plot, that keeps the pages turning.

The main problem is the character of the girl herself. Aside from beauty and guts, she is eminently unlikeable. This makes it hard to understand why someone would waste an entire life pining for her. Whenever Ricardo meets her - first as a revolutionary freedom fighter, later as the wife of a horse trader and the moll of a Japanese mafia boss - she brings nothing but agony and disappointment.

The only explanation is that Ricardo suffers from a monumental Madonna/whore complex. Certainly, his sanctimonious romanticism fuels his compulsion to save her, as well as her desire to get away from him. As if to prove his good intentions their sex life remains interminably repetitive regardless of how morally depraved she becomes.

She certainly gets up to some crazy stuff. Eventually, as a result of a sexual perversion perpetrated by the Japanese gangster, she suffers deep psychological and physical damage - and here I finally lost patience. A book that, without the slightest trace of irony, punishes female ambition and sexual freedom with such a spectacular lack of originality is just too heavy-handed for me. If it were by Jackie Collins, it wouldn't matter; but from Llosa it is deeply dissatisfying.

The Bad Girl by Mario Vargas Llosa

translated by Edith Grossman

Faber, £17.19; 352pp

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