"Don" Jon (writer-director Joseph Gordon Levitt) likes to masturbate. But he can't do it without porn. Lots and lots of porn. So the young, handsome bartender makes plenty of time for it in his exactingly compartmentalized daily schedule. For this Jersey Shore-ish guido, it's not Gym/Tan/Laundry, It's Porn/Gym/Porn/Swiffer/Porn/Church/Porn/Family/Porn/Porn.
Jon likes sex with girls he meets at the bar, too, and he gets plenty, but he finds himself sneaking away during the after-cuddling to check out the Internet women who'll do anything he wants. Into his structured existence glides Barbara (Scarlett Johansson, strongly self-possessed, even while doubling down on her "Look at all these marble columns!" character from SNL), a woman with some sexual ideals of her own: she likes terrible romantic comedies. She thinks male/female relationships should mimic them, that fairy tale scenarios and rigid gender roles should rule all human interaction. She hates the idea that Jon cleans his own apartment with an obsessive enthusiasm. "It's not sexy," she tells him before shutting down any more conversation on the matter. And she despises porn. Real men aren't supposed to go near it. Guess how long she and Jon will be together?
There's a heightened sense of cartoonishness happening in Don Jon. The thick accents, the way Jon's weekend dinner with his family (dad Tony Danza, mom Glenne Headly, silent sister Brie Larson) invariably involves spaghetti and undershirts, a tonal approach to working-class aesthetics that dances brazenly on the edge of condescension, all of it threatens to sink the film's admirable satire of regular horny dudeness. Its truth, that pop culture ruins functional relationships by pandering to everyone's dumbest instincts (and its less palatable truth, spoken by Levitt: "Every guy looks at porn every day.") is frequently upstaged by those dumb instincts.
Julianne Moore emerges in the second act, middle-aged and makeup-free, a character with no real function than that of the clear-eyed dose of real womanhood that Jon might consider following around like a puppy if he knew what was good for him. She's less person than plot checkpoint, but she's still one you're happy to see, if only to remind you that there's life outside of hair gel, heavy eyeshadow and extreme yelling.
In the end Don Jon is funny until it's not, smart until it begins repeating itself, wise when it feels like ignoring its own impulse to privilege the obvious over the subtle and sexy when it decides to stop hating sex. Like watching strangers hump on the Internet, it's almost what you want it to be.