No matter her audacity, the Material Girl is only as good as her material, and Madonna has only half a movie here.

“W.E.” is the second film that the singer (and sometime actress) has directed. It’s a definite leap forward from 2008’s “Filth and Wisdom,” her mangy maiden directorial effort, but suffers from a faulty structural conceit that undercuts and fatally weakens the movie.

(“W.E.” opens tomorrow, Dec. 9, in Los Angeles for a one week, Oscar-qualifying run. It will then receive a wider release Feb. 3, just in time for -- coincidence? I think not -- Madonna’s halftime appearance Feb. 5 at the Super Bowl.)

The movie’s titular initials stand for Wallis and Edward, as in Wallis Simpson and Edward VIII, the British king who in 1936 gave up his crown “for the woman I love,” a twice-divorced American socialite.

“W.E.,” with a screenplay by Madonna and longtime collaborator Alek Keshishian, is a revisionist take on this oft-told, true-life tale (mostly in TV movies), one that puts the focus on and is sympathetic to Simpson.

But that’s only half the film. Intercut with the period story of Wallis (Andrea Riseborough) and Edward (James D’Arcy) and their surreptitious romance and subsequent empty social whirl of a life in exile is a logy parallel story set in 1998. It revolves around Wally Winthrop (Abbie Cornish), an unhappily married Manhattan socialite who becomes involved with Evgeni (Oscar Isaac), a Russian émigré who’s a guard at Sotheby’s auction house. They meet when Wally spends day after day wandering languorously through Sotheby’s pre-sale exhibition of items that once belonged to the Duke and Duchess of Windsor. (Edward died in 1972 and Wallis in 1986.)

Eventually, Wally and Wallis manage to cross over into each other’s worlds and interact briefly, with the older woman advising the younger one based on life lessons she has learned the hard way.

The 1930s part of “W.E.” overlaps partially in events and time frame with last year’s The King’s Speech. But unlike that movie, its political point of view is tepid (Madonna has Wallis and Edward issue preemptive dismissals of talk that they are Nazi sympathizers and vaguely hints that Edward’s do-gooder social impulses may have caused conservative politicians to plot against him). The result is characters who are little more than elegant mannequins swathed in beautifully cut silks and satins, all shimmering surface.

Still, the Wallis-Edward story is the one that holds a viewer’s interest, partly because it presents compelling historical events but mostly because the talented, slinky Riseborough manages to make Wallis’ brittle charm fascinating and even seductive.

Every time, though, that the movie switches to whiny Wally’s story, a viewer groans. There is nothing remotely interesting about this character.

What was Madonna thinking? Wally is Debbie Downer in more expensive clothes (and lingerie) and a fancier apartment but she’s still no one you want to spend time with.