He means "bad" in the good sense, of course - at least at the beginning. It is the summer of 1950, a time our narrator, Ricardo, will remember as the happiest of his life. Living in Miraflores, a smart neighbourhood of Lima, he and other teenagers enjoy a lively social life, discreetly presided over by priests and maiden aunts.
Their life is a round of making out and breaking up at parties. This is also the historic moment when "everyone stopped dancing waltzes, corridos, blues, boleros, and huarachas because the mambo had demolished them".
Into the midst of such innocent fun strolls Lily, a sophisticated Chilean of 15 who has a scandalous way with her hips when dancing and tells jokes so risqué they make the Miraflores girls blush. "What a girl!" chides Ricardo's aunt.
Ricardo is smitten and dreams of a future in which he can marry Lily and move to Paris. Then, at one of the parties, his paramour is dramatically unmasked: it turns out that Lily is not Chilean and may even be lower-class.
This is when we learn that, quite apart from her provocations on the dance floor, Lily can be "bad" in other ways too. She tells dreadful lies - the kind that make you gasp and stretch your eyes - and she is always pretending to be something she is not. Since he never learns her true name, Ricardo calls her the "bad girl".
The next time they meet, Ricardo is working as a Unesco translator in Paris and Lily has metamorphosed into Comrade Arlette, a revolutionary in training. Later she will be the wife of a diplomat, then of a businessman with an interest in racehorses, then she becomes a kind of geisha, trafficking aphrodisiac remedies for a Japanese honcho.
In each incarnation she crosses paths with Ricardo, whose life is a picture of stability by comparison, except that he cannot form relationships, because he is doomed to love only the Bad Girl. And this he does with passion, in spite of her coldness in bed.
"She allowed herself to be kissed from head to toe, maintaining her usual passivity, and she heard, like someone listening to the rain, Neruda's 'Material nupcial', which I recited into her ear, along with my stammered words of love: this was the happiest night of my life."
Mario Vargas Llosa has a deserved reputation as the intellectual powerhouse of Latin American literature, but I prefer him when he is funny. There is more flesh on the bones of his comic creations.
That is not to say that this is a simple comedy: Ricardo's infatuation is alarming, and there is tragedy in the Bad Girl's cruelty and self-abuse, and in her assertion that money represents "the only happiness you can touch".
The novel contains serious criticisms of Peru's treatment of its poorer citizens. It is also a clever homage to Flaubert, of whom Vargas Llosa has often written admiringly.
All the same, there is a wonderful bolero cheesiness about some of the scenes, especially as Ricardo learns about each new identity of his lover in increasingly outlandish ways.
On one occasion he spots her in a photograph of racegoers at his friend's apartment. On another, a mute neighbour informs him she has telephoned him via a scribbled note on the slate hanging round his neck. If this were going to be a film, you'd definitely want Peter Sellers in it.
The same humour and good naturedness that characterised Vargas Llosa's Aunt Julia and the Scriptwriter are written into almost every line of this novel (I think you have to be good natured to describe Newmarket as "mysterious"). Edith Grossman's translation conveys Vargas Llosa's tone marvellously well.
I have some reservations. The Bad Girl's stated ambition - to be "your lapdog, your whore" - strays uncomfortably into male fantasy, as does the retribution visited on her. But that is the story Vargas Llosa wanted to tell, and he does it brilliantly.
I put the light out at midnight with 30 pages still to go. Two hours later I had to put it back on, to find out what happened to the Bad Girl.
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