The Gatecrasher, by Madeleine Wickham.
I was a little disappointed when, while writing the review of "Remember Me?", I wikipedia'ed the author and found that Sophie Kinsella is actually a pseudonym, and the author has a whole other life writing more serious fiction as Madeleine Wickham (which may or may not be her real name either). One has a certain impression of one's authors, a little fantasy of a sweet young lady giving up her day job and plugging away at one slightly-autobiographical novel or so each year, and becoming a surprise success. Only to find out she has been writing longer and much more seriously all along. One does not like to have one's bubble burst.
Fans may be interested to know that The Gatecrasher will be re-released in May (with Kinsella's name prominently displayed on the cover - you see, the fame of the latter has overtaken that of the former). And Kinsella recently conducted a book reading in Second Life which is, I take it, the next Big Thing.