I loved the book very much (except of the last page, which felt strange, to say the least).
The characters feel real, even though they probably were supposed to symbolize two different sides of human nature, two types of personalities (Good and Evil, in Nothomb's terms, but that's subject to the discussion).
It is perfectly believable that story like that happens - nice and lovely "bookworm" Blanche's world clashes and crashes when she meets and befriends Christa, who is all about the physical side of life - boys, parties and excitement. Yes, appearances are deceiving and the relationships between girls are complicated - friendship? Possible. Hate, jealosy? That, too. Conflict? You bet. That's how it happens in the real life, even though Nothombs brings it to the full absurd level. Realistic to sur-realistic...
I would give the book 5 stars, if not for the ending, which seems to be written as an afterthought and feels wrong. And I don't mean the logic of what happens, but rather the way the events are described. (Trying hard to not give spoilers).
Still, out of all books by Nothomb that I have read so far, this one is definitely my favourite and worth reading. If nothing else, it would make for a heated book club discussion.