Twenty-one-year-old Jersey girl Annie Braddock (Scarlett Johansson) is just out of college and would like to pursue anthropology, but suddenly finds herself nanny to a little boy named Grayer (Nicholas Reese Art), the scion of an immensely rich Upper East Side family. Referred to simply and demeaningly as “Nanny,” she finds that her duties extend beyond child care, making her a virtual slave to Grayer’s monumentally self-absorbed mommy (Laura Linney), whom Annie refers to, simply and demeaningly, as “Mrs. X.” Back across the Hudson River, Annie’s own mommy (Donna Murphy) is a hard-working nurse, forever worrying about a daughter who finds it necessary to conceal her lowly vocation from her.

Like The Devil Wears Prada, The Nanny Diaries film improves on its glossy book source with a more forceful point of view and dramatic arc, thanks to writer-directors Shari Springer Berman and Robert Pulcini (American Splendor). Their screenplay wittily points up Annie’s anthropologist career yearnings by framing the movie with tableaux from the American Museum of Natural History depicting the various class tribes of Manhattan, as well as adding touches of Mary Poppins whimsy which actually charm. The fact that Annie finds herself an American-born, white, educated exception in the nanny field is not lost here. The dialogue is fast and pungent, the pacing is suave and the production has a burnished glow to equal any of Woody Allen’s most alluring odes to monied Gotham.

Johansson and Linney make their strongest outings in some time, redeeming a lot of indifferent film appearances of late. Johansson is a fit heir to those classic working-girl comediennes of the ’30s like Jean Arthur and Ginger Rogers, who found themselves agog in ritzy surrounds. She downplays her succulent beauty with darker hair, but that husky voice retains its special prole appeal and her obvious brains and heart win total sympathy from her first scenes. Linney makes her most vivid screen impression yet, reveling in Mrs. X’s glamorous bitchery, and looks an elegant treat in costume designer Michael Wilkinson’s cannily chosen couture ensembles. Mrs. X’s selfishness and tightly wound angst are both appalling and hilarious, yet Linney also delineates the character’s desperate, married frustration so skillfully—her voice has deeper notes of raging sadness in her spousal confrontations—that it’s impossible to completely despise her. Paul Giamatti is forcefully convincing as “Mr. X,” the perfect asshole Captain of Industry, who never tires of reminding everyone that it is through his labor that all this cushiness is possible in the first place. The filmmakers amusingly build up his entrance in this unlikely role, subverting his nebbishy American Splendor persona and giving him his own egomaniacal Town Car glamour.

Special mention must be made of casting director Ann Goulder, who, from top to bottom, has done a flawless job, filling the movie with an arsenal of newcomers and New York stage veterans. Little Art is adorable, and—miraculously—not gratingly precocious, as Grayer. As Annie’s romantic interest, Chris Evans, with the eyelashes of a llama, lives up to his given nickname “Harvard Hottie,” and could well find himself the new Luke Wilson/Jake Gyllenhaal go-to guy. Alicia Keys is radiantly appealing in her slim role as Annie’s funky Eve Arden sidekick. Donna Murphy, although a bit too glam to be wholly believable as a harried caregiver—she seems to go to the same spa as Mrs. X—gives the film some accurate, necessary grounding. Julie White, who won a Tony for her hilarious turn in The Little Dog Laughed, brings her deliciously intense comic energy to the part of a nanny-employer group counselor. Cady Huffman, James Urbaniak and even Broadway’s current Mary Poppins, Ashley Brown, make striking appearances, even momentarily.