In a prologue, we learn that timid widow Diane (Diane Keaton), high-powered hotelier Vivian (Jane Fonda), federal judge Sharon (Candice Bergen) and restaurateur Carol (Mary Steenburgen) are fast friends who've been meeting for their regular book club since the '70s. Two of them are Stanford grads, and their first book was Erica Jong's Fear of Flying.

If anything, one might expect these seasoned, savvy women to have a spirited debate over whether E.L. James' whips and cuffs are more or less revolutionary than Jong's championing of the "zipless fuck." Instead, they blush and giggle over Christian Grey as if nothing so scandalous could ever have been published in their youth (which, lest we forget, was the 1960s, not the 1860s).

Frankly, this inciting incident makes one wonder if writers Holderman and Erin Simms actually read James' opus. But the adventures of the four boomers, once Fifty Shades inspires them to change their sexual and romantic status quos, are still reasonably entertaining. Carol tries to rev her husband's motor, only to find he's more interested in motorcycles. Divorced Sharon experiments with online dating, Vivian reconnects with an old flame (Don Johnson), and Diane starts a tentative romance with an airline pilot (Andy Garcia).

While some of the script's one-liners fall flat ("So I'm screwed ... or not screwed, as it were," Carol laments), others are actually pretty snappy. "You don't have a sad story because you're rich," Diane tells her beau. It's the film's sole acknowledgment of how financially comfortable all these characters are, but that's more acknowledgment than you'll see in most rom-coms.

Plenty of screen time goes to Keaton and Fonda, who play caricatures of their off-screen personae: One is a mouse, the other a man eater. While Fonda's dalliance with Johnson never generates the requisite witty sparks, Keaton gets the most laughs in the movie. Her sheltered character squeaks, flutters and dithers through the awkwardness of courting, channeling classic screwball comedy with equal portions of plaintive helplessness and sly wit.

One of the film's smarter subplots concerns Diane's relationship with her two daughters (Alicia Silverstone and Katie Aselton), who treat her like a doddering oldster, insisting she come live under their protective eyes ("We redid the basement for you!"). It's common to see seniors gently mocked and condescended to in pop culture, but less common — and welcome — to see younger folks mocked for infantilizing their elders.

It's also ironic, considering that Book Club does a certain amount of infantilizing of its characters in the name of comedy. The film offers way too many tired, standard gags about dry spells and Spanx and Viagra. But once it's gotten through those, it does have a certain respect for its characters as romantic and, yes, sexual beings. Sharon gets to experience hookup culture, Vivian discovers emotional intimacy, Carol reaffirms a lifelong bond, and Diane figures out how to live for herself and not others.

They don't all have to have the same happy ending; half the fun of a book club is finding out what different messages readers can take away from the same story. If only these women had been inspired by a better one.