From the four films I've seen so far by malle (the others being "Damage", "Lift to the Gallows" and "Zazie dans la metro") this one seemed clearly the strongest, and the closest to a masterpiece. Besides the marvelous photography I thought the main performance brilliant. I've rarely seen a more gripping and touching love affair depicted on screen. Contrary to wpqx I could almost always feel his desires and emotions, and identified with him from the beginning. Of course he isn't a likable character, and presented in an ambiguos way, but t is his total lack of expressing himself in a way that can be understood by his surroundings that is fascinating. he's locked in, and has his own beliefs, while on the outside he seems to conform. But the conformism is only a scheme, as well as an ego thing (of finally being accepted). He's more like an invisible person, because he is almost the only one who's alive, searching for something, while all the other characters are locked in their views of the world. Only through France he feels in the end understood. I loved the ending, as it seemed quite positive to me. It is clear that such a person cannot live in the restricted society that surrounds him. It is only in the end's out of the norm days and weeks that he seems to find peace. 
The love of Lucien towards "France" was for me filled to the brim with (restrained) passion, something Malle manages to pull off quite effectively also in some of his other films (Damage, Lift to the gallows). 
I think I now maybe like it even more than when I initially saw it.
Imo a must see film.