The rich are getting richer, but that isn't buying them much love from the movies; it may only be upping the hatred. In The Nanny Diaries, based on Emma McLaughlin and Nicola Kraus' I was a yuppie nursemaid chick-lit novel, Annie Braddock, a suburban New Jersey girl just out of college, falls into what is, for her, an innovative mode of delayed adulthood: She decides to spend the summer working as a nanny in New York City. Annie has vague notions of becoming an anthropologist, but beyond that she has little idea of who she wants to be. Scarlett Johansson, with her guarded, people-pleaser softness and slightly morose carnality, plays her as a born observer, an unformed young woman who embraces her new job almost voyeuristically, as a window onto the adult world or, at least, a certain obscenely wealthy Manhattan sector of it.
Annie gets hired to look after Grayer (Nicholas Reese Art), the spoiled but basically sweet 5-year-old son of a couple she refers to simply as ''the X's,'' who live just off Fifth Avenue in an apartment that is pure, sprawling, old-money-flavored real estate porn. Mrs. X (Laura Linney), a vainly prattling porcelain-doll narcissist, does nothing all day but shop, lunch, tend to her wall of designer shoes, and go to ''meetings'' with other social X-rays. They're mommies who don't want to be mommies or, at least, don't want to spend more than five minutes at it, apart from fretting over which private school their tot genius is going to get into (or, in the case of culinarily correct Mrs. X, whether Grayer eats tofu or peanut butter). They treat their kids as designer accessories.
Actually, Mrs. X does one additional thing: She complains a lot. Whatever Annie does, it's never good enough, and Mrs. X's way of addressing her simply as ''Nanny!'' is the ultimate demeaning sneer. She might be talking to a domestic robot. The Nanny Diaries has nothing but sympathy for poor, put-upon Annie as she cleans up kiddie vomit in her upper-class prison, but it's less interested in her as a character than it is in the elite social pathology of the people she's working for. This is the same strategy that worked so well in The Devil Wears Prada, which had the daring to portray Meryl Streep's editrix monster as a figure of artfully malign fascination. Laura Linney, a great actress, with an erotic danger Streep has never possessed, could surely have done something similar, but The Nanny Diaries turns her into a pale WASP zombie the Stepford Bitch.
Mr. X (Paul Giamatti) is an even coarser piece of work. He's a blustery mergers hotshot, with piggy eyes that peer out from arty metal spectacles, a cell phone soldered to his ear, and a mistress he does such a bad job of hiding that it's as if he enjoys tormenting his wife. (His sadism is at least a break from his indifference.) Hooked on her husband's money, Mrs. X lives in denial, to the point that when she finds a strange negligee in the laundry, she orders the nanny to ''admit'' it's hers. Linney hints at the sadness beneath Mrs. X's waxworks existence, but it's never more than a hint.
The Nanny Diaries was written and directed by Shari Springer Berman and Robert Pulcini, who previously made the marvelous, lower-depths comedy American Splendor (2003). You'd think that the filmmakers who caught the life of the squalid, lumpen crank Harvey Pekar with such transporting humanity would try to do something similar for the superrich. The movie comes on as a cheerful anthropological satire, opening with an amusing series of faux dioramas in the Museum of Natural History (they include New York types like ''Tribeca Fashionista'' and ''Park Slope Lawyer''). But Springer Berman and Pulcini embark on their anthro-expedition to the Upper East Side wielding poison daggers. Their sympathies are still with the working class didactically so. Yes, there are wealthy New Yorkers as toxic as the X's, but by making them so one-dimensional that it threatens to strain the word dimension, The Nanny Diaries becomes as flaccid and predictable as something you'd expect from Hollywood hacks.
What the picture keeps dancing around is that Annie, in her way, is nearly as privileged a person as the X's. She becomes so attached to Grayer that she can't leave him, but the other nannies she gets to know, most of whom are nonwhite, could scarcely afford to think of their jobs as a social ''experiment.'' The more that Annie stresses, speaking to us in her mopey voice-over, whining about the perils of home day care to the preppie dreamboat she dubs ''Harvard Hottie'' (Chris Evans), the more you want to say, ''If you don't like it, girlfriend, then quit!'' For a light comedy, The Nanny Diaries turns out to have an off-putting theme. It glorifies the romance of slumming.