"The Nanny Diaries" is a nice late-summer surprise, a big-screen adaptation of a best-selling novel (by Emma McLaughlin and Nicola Kraus) that, for whatever reason, has shifted release dates more than once and hasn't been given the promotional push it deserves. Such signs are rarely good in the land of Hollywood and frequently suggest that a studio has a stinker on their hands. "The Nanny Diaries" is far from a failure, though. In fact, it is acerbic and cutthroat in all the right places, along with truthful, savvy, and consistently entertaining. One would be safe to call the film a dark, satirical comedy above all else, but underneath the humor is a human sadness bordering on tragedy that soaks up many of the laughs. This is as it should be, in a motion picture that sets an uncompromising gaze on a sort of shallow, privileged domestic lifestyle that is likely more prevalent than people care to admit.

Annie Braddock (Scarlett Johansson) is a recent college grad (and working-class New Jersey native) whose plans to pursue business and anthropology are waylaid by cold feet and a fluke offering to become a nanny for an Upper East Side family. As a means of getting to move into New York City and earn some solid wages as she figures out what to do with the rest of her life, Annie expects that working for Mr. X (Paul Giamatti) and Mrs. X (Laura Linney) and taking care of five-year-old son Grayer (Nicholas Reese Art) will be a cinch. Instead, it becomes practically a 24-hour job as she substitute parents the young boy while his philandering, workaholic father doesn't give him the time of day and his unemployed mother busies herself with sleep and piddling banquets and fundraisers. When Annie finds herself emotionally attaching herself to Grayer, and vice versa, she is faced with some tough decisions involving her future.

Written and directed by Shari Springer Berman and Robert Pulcini, "The Nanny Diaries" is tart and intelligent, a sort of tell-all exposé as seen through the eyes of a young woman befalling the title occupation. Annie might still be undecided on what it is she wants to do for the long-term, but she is also knowledgeable enough to view those around her for what they stand for, imagining various strangers and circumstances she encounters as if they were exhibits on display in New York's Museum of Natural History. This comedic edge carries over to the characters' names; Mr. and Mrs. X are generalized as such so that they stand for the whole of parents like themselves, and Annie labels her prospective boyfriend Harvard Hottie (Chris Evans) as a way of distancing herself from a relationship that could get her fired if she pursues it. Later, when Annie is forced to give up her rare free night so that she can attend a clueless and delusional upper-crust meeting about extending the lines of communication between mother and nanny, the results are bitingly funny.

Scarlett Johansson (2006's "Scoop") is irresistible as Annie Braddock, carrying the film and doing a damn good job of it. Johansson remains one of the best of her generation of actresses, essaying an intuitive, wise, powerful, and yet still feminine, brand of heroine that mixes elegant old-Hollywood looks with refreshingly modern sensibilities. Following the bright and patient Annie from page one is a treat with Johansson in the role, made increasingly satisfying when things reach a boiling point and she finally speaks her mind to the people most in need of a reality check. Her motherly bond with Grayer, played with an exceptional unaffectedness by talented child performer Nicholas Reese Art (2005's "Syriana"), is the true heart of the story, and also the reason for why Annie is so conflicted about walking away from the thankless, high-demand job.

"The Nanny Diaries" is difficult to dislike but also easy to be enraged by. The harsh but realistic depiction of high society types who treat their own children like accessories rather than people gets scarily bleak, the emptiness within such a life captured with sobering clarity. Laura Linney (2005's "The Exorcism of Emily Rose") is brilliant as Mrs. X, a textbook example of the kind of woman who doesn't work, gets her cash from her distant moneybag husband, and yet still can't seem to find the time to do anything for herself or, at the least, be a loving parent. Linney is appropriately icy and spiteful in her treatment of Annie, but figures a way to bring humanity to the role as she naively fools herself into believing her life is as perfect as she thinks it should be. As Grayer's dad, Mr. X, Paul Giamatti (2006's "Lady in the Water") is great at being despicable, disappearing into the irredeemable part of a man who has traded his soul and compassion for power and paychecks. Throughout the film, the viewer is nagged by an intense worry about poor Grayer's welfare as he is caught in the middle of nannies who ultimately leave him and blood parents who might as well be out of the picture.

"The Nanny Diaries" does extremely well at juggling a tone that is light when it needs to be light and serious when it needs to be serious. Mawkish emotions are traded in for well-modulated, low-key authenticity, and the accompanying soundtrack and music score compliment scenes without overpowering them. If anything rings false, it is the romance between Annie and Harvard Hottie. Chris Evans (2007's "Sunshine") portrays the role all wrong, emitting a smug aura to his personality that could quite possibly turn him into another Mr. X ten years down the road. Annie should be turned off by him, but isn't, perhaps because films like this require a love interest. Nonetheless, Harvard Hottie could have been written with more sweetness and less cockiness. It's a minor quibble, but one that warrants mentioning since virtually everything else surrounding it is pulled off with such grace. "The Nanny Diaries" is highbrow mainstream fare without a hint of smarminess, that rare and enjoyable slice-of-life that doesn't often get released from major studios. This alone is something worth celebrating.