"The Last Mistress" is one of those obsessive sex melodramas that the French do so well. But it's much more than that.

Set in the 1830s and based on Jules Barbey d'Aurevilly's novel from around that period, this sumptuous production is a wry examination of changing social mores and a sophisticated study of the politics of desire from both male and female points of view.

Asia Argento is La Vellini, an unapologetically scandalous Spanish courtesan who has carried on a tempestuous 10-year affair with Parisian ladies' man Ryno de Marigny (Jolie-lipped newcomer Fu'ad Ait Aattou). But when the penniless lothario marries the beautiful younger aristocrat Hermangarde (Roxane Mesquida), Vellini has no intention of getting out of the picture.

I've made fun of Argento's bad-girl poses in the past. But here she brings complex humanity and spine-tingling poignancy to a calculating, defiant, hurt-beyond-all-reason soul -- while still doing trademark Asia stuff like carnally licking bloody wounds. Aattou isn't quite up to her amour fou-ish level, but he lends unusual depth and intelligence to the role of a roue with good intentions and a heart he can't deny. Claude Sarraute stands out among the film's delightful ensemble of elderly actors as Hermangarde's protective grandmother, who happens to prefer the pre-Revolution days of her anything-goes youth to the rising moralism of the Victorian era.

In her first period piece, writer-director Catherine Breillat refrains from shocking quite as much as she tried to in such controversial works as "Romance" and "Fat Girl." There's still plenty of raw sex in "Last Mistress," though, and Breillat's take on the topic is alive and well - and arguably more cogent than ever.

THE LAST MISTRESS

>Not rated: sex, nudity, violence, children in peril.

>Playing: Town Center 5, Encino; Playhouse 7, Pasadena; Sunset 5, West Hollywood; Landmark, West L.A.; Monica, Santa Monica. In French with English subtitles.

-- Bob Strauss