Producer Ismail Merchant and director James Ivory are famous for their loyalty to their source material. But in 'Le Divorce,' that's too much of a good thing.

Like most Merchant/Ivory films, it features a deep cast and an exquisite sense of detail. And it deals with one of their favorite themes: a culture clash. But in their insistence on accurately reflecting Diane Johnson's 1997 novel, the pair have reached too far. Instead of pruning the narrative to essentials, they try to include everything, leaving characters that never develop and actions that lack motivation.

Working with their regular screenwriter, Ruth Prawer Jhabvala, Merchant and Ivory favor style over substance. The story is set in France, and the film makes use of a variety of impressive locations, from quaint apartment-building courtyards to the Eiffel Tower. But the team behind such literary adaptations as 'A Room With a View' and 'Howard's End' doesn't keep the narrative taut enough to get us more interested in the story than the scenery.

The protagonists are a pair of American sisters, Isabel (Kate Hudson) and Roxy (Naomi Watts). Isabel goes to Paris to visit Roxy, who's married to a French artist, Charles-Henri. Isabel arrives just in time for his announcement that he's in love with another woman.

Although Isabel is sympathetic, she misses the point of her sister's heartbreak. Overcome by the romantic Parisian atmosphere, Isabel finds herself caught up with a married man (Thierry Lhermitte).

Meanwhile, still hoping to save her marriage, Roxy is a loyal attendee at the weekly family dinners hosted by her husband's mother (Leslie Caron), a passive-aggressive matriarch who tsk-tsks Charles-Henri's infidelity but encourages him to get his fair share of the joint property.

This would be enough for a movie, but the filmmakers aren't done. Soon Roxy's parents (Stockard Channing and Sam Waterston) show up, not to provide emotional support but to make sure the divorce settlement doesn't include a painting that is a family heirloom. Rounding out the tangled mess is Matthew Modine, who pops up as the vindictive husband of Charles-Henri's lover.

Fine actors all, Channing, Waterston and Modine are reduced to playing stereotypes. Caron's character is one we'd love to see more of, but there isn't enough time in the busy script.

The lead actresses seem shortchanged, too. Neither Hudson nor Watts brings much of an arc to her character. By the time the story ends, we're not sure if either Isabel or Roxy has learned anything.

The Merchant/Ivory fascination with the trappings of the upper class comes into play at the country estate of Caron's character. And their reputation as first-class filmmakers is evident in the casting, which includes several notable performers -- among them Glenn Close and Bebe Neuwirth -- in small supporting roles.

The humor is sophisticated, the film is shot smartly, and the script is seasoned with insights about two cultures caught in a love-hate relationship. (Shot before the U.S.-French falling out over the Iraqi war, the film includes several lines that take on an unintended double meaning.)

Despite all these attractive trappings, however, the film comes up short on insight into its characters. 'Le Divorce' leaves us feeling unattached.

Le Divorce ** 1/2 out of four stars

The setup: Even though Naomi Watts is crushed when she learns that her husband is having an affair, her sister (Kate Hudson) is drawn into an affair with a married man.

What works: Leslie Caron as Watt's manipulative mother-in-law.

What doesn't: A subplot involving an irate Matthew Modine is embarrassingly shallow.

Great line: 'He's married -- whatever that means nowadays.'

Rating: PG-13; profanity, sexual references

Jeff Strickler is at jstrickler@startribune.com.