Make no mistake: The new movie by Joe Swanberg is not a romantic comedy. If you waltz into Drinking Buddies expecting the formulaic satisfaction of a rom-com by Nora Ephron, you will be violently disappointed. You will throw your popcorn at the screen and demand your money back.

Starring Olivia Wilde and Jake Johnson as Kate and Luke, co-workers at a hip brewery, Drinking Buddies is about the emotional tangles that occur between men and women of a certain age — men and women whose lives have yet to calcify into the mortal routines of career, marriage and other commitments of a supposedly adult nature. As the drinking buddies of the title, Luke and Kate have a seemingly carefree relationship, given to after-work beers and lots of laughing and flirting. That laughing and flirting has boundaries, sort of: They are both in relationships. Luke’s fiance, Jill (Anna Kendrick), is pressing for a wedding date; Kate’s boyfriend, Chris (Ron Livingston), is a literary drip whose emotional engagement is something less than passionate. Fear and indecision, however, perforate boundaries, and, at least for Luke, the grass begins to look greener on the other side of the monogamous fence.

Confusion ensues. It gets complicated.

Swanberg, who wrote and directed Drinking Buddies, is a founding member of the recent mumblecore movement. Mumblecore movies were low-budget affairs. Using handheld cameras, mumblecore directors shot situational slacker dramas improvised around a bare-bones story employing amateur actors and virtually no fireworks in the way of lighting, soundtracks, make-up, etc. These movies are sexually explicit and stutteringly awkward, and they contain the emotional resolution of a Samuel Beckett play. For this reason, mumblecore proved a mixed bag, often maddeningly prosaic but intermittently given to bright flashes of excruciating authenticity.

With Drinking Buddies, mumblecore has stopped talking out of the side of its mouth. Whether you want to listen to what Swanberg has to say depends on your tolerance for art that practices the slow burn. Way back last century, before we all developed the attention span of gnats, American directors like Robert Altman and John Cassavetes made multi-talent ensemble dramas that were loose and baggy epics of gritty realism. Cassavetes especially seemed to let the camera run about five minutes past where most mainstream movies chopped the scene. The results were by turns explosive, exasperating and revelatory.

Swanberg is no Cassavetes, but Drinking Buddies is an admirable addition to the tradition of cinema that expects us not to have pat expectations, and that rewards our patience by telling us truths about the unspectacular but ever-dramatic everyday lives most of us lead.

DRINKING BUDDIES: Directed by Joe Swanberg. Written by Joe Swanberg. Cinematography, Ben Richardson. Editing, Joe Swanberg. Starring Olivia Wilde, Jake Johnson, Anna Kedrick, Ron Livingston and Jason Sudeikis.  Burn Later Productions, 2013. R. 90 minutes. Three and a half stars.