The main character in The Devil Wears Prada — Lauren Weisberger’s ingeniously titled, tiresomely self-entitled roman à clef about her year of servitude at Vogue magazine — is young Andy. She’s an assistant with high-minded journalistic dreams stuck toiling for shallow Miranda Priestly, the bitch boss from hell. But in the move to the big screen, the less interesting little girl, underplayed smartly by Anne Hathaway, gets shoved aside to make room for a marvelously wicked Meryl Streep. And what was sold as silly chick lit all of a sudden turns into a delightfully knowing and sympathetic portrait of working women, elevated at every turn by an actress doing some of her best comedic work and clearly having a ball.

With a fierce swoosh of silver hair and a fearsome voice that never rises above an icy purr, Streep’s Miranda could reduce any of film’s famous Mob bosses or gunslingers to a puddle if she so much as flicked her wrist in their direction. Her scathing bite of dismissal — ”That’s all” — can reek of disgust or boredom or fatigue or, in one breathtaking moment where Miranda’s cool mask of composure is stripped away, resignation. One of the best-written and -played scenes of this whole snappy affair is when Miranda takes Andy to task for snorting in disbelief as Runway editors struggle to decide between two similar-looking belts. In an expertly constructed 75-second monologue, Streep sneers at her foolish assistant’s ”lumpy blue sweater,” coiling one of the offended belts in her hand like a whip while she gives Andy a master class in the very real business of fashion. Where Weisberger blithely mocked that world, screenwriter Aline Brosh McKenna and Streep study and salute. Without taking the fizz out of this party of clothes and shoes and New York City scenery, the movie gracefully examines the price a powerful woman has to pay for her success. It also offers a wise rebuke to the parent-subsidized upstarts who come waltzing into a workplace at 23 expecting a break. ”You want to know why she doesn’t kiss you on the forehead and give you a gold star on your homework,” says Miranda’s second-in-command, played with divine smoothness by Stanley Tucci, to a pouting Andy. ”Wake up.”

It’s a shame, though, that a movie that lovingly celebrates accessories arrives so disappointingly dressed on DVD. The extras are unexciting; Streep shows up for just a glimpse. And who can blame her, after she’s shown trying her best in an inane interview on one of the lukewarm featurettes: ”How can I answer the question ‘Why is fashion so important in this film?”’ She looks off, amused, trying to keep a straight face. ”Honestly,” she admonishes with a patient laugh. That may have been Streep’s gracious way of saying ”That’s all.”