There’s no cinematic rule that requires fealty to a book adapted as a movie, but just because you can muck about with the text doesn’t mean you should. Slavishness to a source doesn’t guarantee success, and radical rethinkings do sometimes resonate (see Alexander Payne’s “About Schmidt”).

But splitting the difference practically ensures failure; director Mira Nair proves that with her new version of Thackeray’s “Vanity Fair.”

Ms. Nair gets some of it right. Her film is studded with old monuments – not just in the form of decrepit grand houses, but also in the persons of several cherished actors, Eileen Atkins, Bob Hoskins, Jim Broadbent, and Geraldine McEwan among them. What Ms. Nair and screenwriters Matthew Faulk, Mark Skeet, and Julian Fellowes fail to capture is the deliberate pacing, a hallmark of 19th-century novels necessary for the deployment of the plot.

Rather than progress in a suitably stately fashion, this film lumbers awkwardly, lingering where it shouldn’t and then fast-forwarding in compensation. Ms. Nair only exacerbates the dislocation by refusing to age her actors, an absurd choice in general and downright laughable in the case of Gabriel Byrne’s Marquess of Steyne, who in some 30 years avoids both gray hairs and wrinkles. Indeed, time and place are so haphazardly marked here that many viewers may not realize that this is the era of the Napoleonic Wars.

An equal blunder comes in (mis)casting Reese Witherspoon as the story’s ever-crafty, frequently sure, ultimately benighted heroine, Becky Sharp – a character previously portrayed on the screen by such paragons as Minnie Maddern Fiske, Miriam Hopkins, and Myrna Loy. Ms. Witherspoon can certainly play the schemer, as anyone who’s seen “Election” or even “Legally Blonde” can attest. It’s her attempts to convey sweetness that seem phony. If the director wanted to make Becky Sharp more sympathetic, she should not have picked Ms. Witherspoon.

Others fare better, especially the brilliant Ms. Atkins. Her Matilda Crawley keeps glad company with Mr. Hoskins, as her brother, and Ms. McEwan, as fussy Lady Southdown. And Mr. Broadbent, thanks to his enormous range, is rightly a veritable fixture in English period pictures these days. Of the younger set, James Purefoy (as hunky Rawdon Crawley), Rhys Ifans (the long-suffering William Dobbin), and Jonathan Rhys-Meyers (born to play George Osborne) stand out.

Though this is a sumptuously made film, an occasional bizarre spectacle undercuts the production. Similar damage is done by Mychael Danna’s curiously exotic and entirely inappropriate score. Apparently, vanity is not just a hurdle for the characters in this movie, but for its creators as well.