The pre-release posters for Mira Nair’s adaptation of “Vanity Fair” prominently announce “On September 1, A Heroine Will Arise!”–and therein lies the problem with the lush but misconceived production. William Makepeace Thackeray’s mammoth novel, after all, is subtitled “A Novel Without a Hero”–and he didn’t mean to imply that it was one of the women at the center of things who possessed heroic properties. As rewritten by Matthew Faulk, Mark Skeet and Julian Fellowes and staged by Nair, however, the scheming Becky Sharp has, despite her surname, been given a Hollywood softening job to make her less steely and more likable. She emerges as a spunky, proto-feminist type you’re meant to cheer, and the alteration, along with others that also weaken the original’s bitter flavor, make for a result that’s not unpleasant in a bland Masterpiece Theatre way, but not very faithful to its astringent source either.

The makeover begins early on, when the screenwriters invent an incident in the shabby studio of young Becky’s artist father, which serves not only to establish the pluckiness of the impoverished girl but also gives a slightly sympathetic cast to the figure of the odious Lord Steyne, who appears only much later in the book. The script then lurches ahead to the point where the novel begins, and thereafter offers a (necessarily) streamlined retelling of the linked fates of its two very different female protagonists–the clever, ambitious social-climber Becky (Reese Witherspoon) and the saintly but rather dim Amelia Sedley (Romola Garai). The former, after a failed dalliance with Amelia’s brother Joseph (Tony Maudsley) and a lucky escape from the clutches of her uncouth new employer Sir Pitt Crawley (Bob Hoskins), finds her way into society through the favor of the latter’s rich, worldly sister Matilda (Eileen Atkins), whose support she unfortunately loses by marrying Matilda’s roguish nephew Rawdon (James Purefoy); the two live in genteel poverty which the unscrupulous Becky counters by cultivating both the smitten Steyne (Gabriel Byrne) and Rawson’s easily-duped brother Pitt (Douglas Hodge), who inherits his aunt’s wealth. Meanwhile Amelia’s arranged marriage to the arrogant soldier George Osborne (Jonathan Rhys Meyers) is first threatened by her father’s bankruptcy, and then leads to penurious circumstances when George’s greedy father (Jim Broadbent) disinherits them for wedding without his consent. George also, as it happens, is drawn to Becky–who’s freed from the decision of whether to submit to his advances when the battle of Waterloo intervenes. The widowed Amelia finds herself doomed to a life of poverty, oblivious to the fact that George’s army companion William Dobbin (Rhys Ifans) has always loved her from afar. From this point the plot follows the women’s parallel stories through pregnancies and many changes of fortune; the film is reasonably true to Thackeray in terms of Amelia’s fate, but regarding Becky it follows its established pattern by providing what amounts to a happy ending. Spunk will triumph, it appears.

Still, while this latest “Vanity Fair” hardly does the novel justice (even the 1998 miniseries, with an edgier tone and a Steyne that mirrored Thackeray’s description of a chubbier Nosferatu far better than Byrne’s sleek version does, did a far better job of that), it provides a handsome mounting that should appeal to viewers of the sort of period British drama that airs on PBS; and very occasionally–as in a scene, drawn fairly closely from the book, in which Byrne’s Steyne brutally berates his wife and daughters-in-law–it sounds the proper voice. Nair doesn’t try very hard to overcome the story’s episodic nature, and her pacing isn’t terribly secure, but she keeps things relatively clear, and some may appreciate her giving the piece a kind of personal signature by adding substantially to the Indian elements found (much more sparingly) in the book. (She goes entirely too far, though, in inserting an exotic ballet for Becky to perform before the king.) Certainly Maria Djurkovic’s production design, Beatrix Aruna Pasztor’s costumes and Declan Quinn’s widescreen photography (using Bath as a fine substitute for nineteenth-century London) are all first-class, though Mychael Danna’s music score is a trifle nondescript. The performances are good, if not outstanding, of their type. Witherspoon continues down the Gwyneth Paltrow path, affecting a convincing accent and giving Becky spine, if not the sense of cold ruthlessness Thackeray gave her. Of the others, Atkins is surely the standout; her rude, cagey Matilda will certainly be an audience favorite (and, like Kathy Bates in “About Schmidt,” she’s not afraid to show a little skin). But Byrne is also fine, despite the fact that he’s far too handsome for the role, Hoskins is clearly having a good time playing a rustic barbarian, and Broadbent lends his customary authority to the thankless part of the blustering Osborne senior. Oddly, the younger men in the cast prove less distinctive. Rhys Meyers gets George’s sneer down right, but doesn’t capture his attractiveness, while Purefoy makes a blandly handsome Rawdon, Ifans a droopily wan Dobbin (though, to be fair, the character’s a cipher), and Hodge a prissy Pitt. That leaves Garai, who’s stuck trying to make the simpering Amelia either credible or interesting. She doesn’t succeed.

One would like to be more positive about “Vanity Fair,” but it’s the sort of conscientious but passionless picture that’s easy to sit through but not particularly engaging. It does, however, succeed better than any previous version I’ve seen in showing just how much “Gone With The Wind” owes to Thackeray’s novel; here the story seems almost a Napoleonic-era foreshadowing of Margaret Mitchell’s. The similarity is so strong, in fact, that as Rawdon stalks out of their house after catching his wife with the Steyne, you half-expect him to say (in a scene that Nair shoots, practically begging us to draw the comparison, at the bottom of a stairwell), “Frankly, Becky, I don’t give a damn.” As a matter of fact, if he did, the movie might be a lot more fun.