New York's happening Llama Lounge isn't really the place for a big-boned heifer like Rachel Walsh, fresh off the Aer Lingus flight from Dublin. But with a line of coke buzzing in her veins, her size-eight feet and freckled cheeks are magically transformed into an altogether more glamorous package - like a graphic designer or a spokesperson for Donna Karan.

In fact, Rachel, and her room-mate Brigit, are not without contacts in cool East Village society. There's Daryl of the purple bell-bottoms who works in publishing and knows Jay McInerney, and Carvela, who once gave Madonna a French manicure. So it comes as something as a letdown when the one male wanting "a ride" with Rachel turns out to be Luke Costello, a perm-haired "hairy eejit" from home, covered in denim and the proud possessor of a Lord of the Rings T-shirt.

Fed up with not being invited to parties, Rachel and Brigit decide to throw one of their own. Though some groovily employed people turn up, Rachel ruins the evening by going home with Daryl, a man whose inclinations run to rolling around the floor like a toddler, thumb in his mouth, calling for "mama".

After an encounter like this, it's not long before "Seventies Throwback Luke" starts to look more like "Cool Ass Luke". Rachel finally abandons herself to his scary manly belt and over-tight Levi's, only to blow it a few months later by taking one line of coke too many and ending up in Cloisters - Dublin's answer to the Betty Ford clinic.

In this novel of two halves, switching between life with the addicts and wild times in New York, some sections are jammier than others. And though there are some nice Bridget Jones-like moments in "rehab", with Rachel overdosing on Lion and Fuse bars and learning to live without mascara, you end up skipping chapters for what's happening with Luke, Rachel and the Manhattan skyline.

Most blockbusters don't usually deliver the goods, even when it comes to sex and shopping. So it's a relief to come across a writer as warm and funny as Marian Keyes (bestselling author of Watermelon and Lucy Sullivan is Getting Married). She knows her Donna Karan from her Alaia, and is still young enough to remember what it feels like to travel home scuzzy and slit-eyed from a strange boy's apartment at seven in the morning. And then go to work.