I am prompted to review not based on any passionate feelings for this movie. I tend to agree with those reviewers who did not "feel" Deneuve's portrayal of Lucile in the movie and thus, I think this movie failed. I think in fact all of Sagan's adaptations to film have failed.
But that is why I am adding my review, to disagree with the reviewer who called the original novel "silly." In fact, there is nothing more beautiful and poignant, simultaneously light and heavy, light and dark, as a Francoise Sagan novel. I don't say she is one of the greatest or most profound of French writers even in the 20th century, but she is so far from being silly it offends the senses to hear it; she has a perfect grip of the human heart and its dance with the human mind, and a magnificent grasp of phrasing, enough to convey profundity and round the most incidental of characters that most writers would allow to lay flat.
As this is not a place to review the novel, I will only say in contrast to the film that Lucile's struggle between Antoine and Charles is not passionless nor can it be summed up simply as a "heart vs. head" conflict, although I appreciate this is the easiest way to summarize and is not inaccurate. In short, it gets a 5 from me and not a zero because it is so faithful to the book, and yet, it gets a 5 and not a 10 because (I suspect) the direction and performances were inadequate to the task of explaining the relationships, the everyday, everyman experiences of love &/or heartbreak that Sagan originally put down so masterfully.