Cooper directs Will Arnett in this likable, semi-believable story about a man heading for a divorce who discovers a cathartic outlet in comedy

Comic actor Will Arnett finally gets a straight dramatic role and he’s playing … a comedian. Well, a would-be comedian. But he’s not an outrageously awful or failing one; the point of this film is not the delicious ironic cringe of delusional loserdom, as it is with Arnett’s small-screen roles such as the hopeless magician Gob Bluth in Arrested Development, or the washed-up equine star in the animation BoJack Horseman, or even his scheming figure skater Stranz Van Waldenberg in the movie Blades of Glory.

Arnett plays Alex, a regular guy with a regular job, married with two young kids but unhappily heading for divorce. He discovers standup comedy by performing in an open mic slot one night on a weed-fuelled whim, and finds that audiences love his unfunny but sweetly honest confessional ramblings. And then he kind of improves – but are we supposed to think by the end that he is, in fact, genuinely funny? It’s not entirely clear. And the film, though likable and spirited and nicely acted, isn’t completely convincing on its own terms. It is, after all, intended to be funny on its own account.

Are we required to believe, for example, that Alex is talented at and committed to comedy in the way his wife Tess (Laura Dern) is supposed to have a vocation for coaching volleyball? Or is standup just a cathartic, meaningful episode through which he might pass before returning to his day-job in finance, with which he might honourably support his children but which is never shown and which apparently never supplies any material?

This is a kind of remarriage comedy, directed and co-written by Bradley Cooper who also appears, interestingly awarding himself a classic Arnett-type role: an annoying and grinningly conceited unemployed actor called Balls (is that a first name? Surname? Nickname?).

The film was inspired by an autobiographical anecdote by the British comic John Bishop, who says he semi-accidentally stumbled into comedy one night in the midst of divorce depression. Of course, that anecdote could be like the stories told by tough-guy actors about how they didn’t mean to get into acting, they just went along with their mate to the audition. But in this business it doesn’t have to be 100% true – just entertaining.

It is clear that Alex and Tess’s marriage is dying. It is a slow, agonising implosion due to Tess’s discontent at having given up her thriving sports career to be a stay-at-home mom to the two kids they had via IVF, and Alex’s lack of support for her incipient depression. Their married friend group are not especially helpful: Stephen and Geoffrey (played by real-life marrieds Sean Hayes and Scott Icenogle) are secure but the appallingly immature Balls and his smart, sharp-tongued wife Christine (Andra Day) have difficulties of their own.

What all these people have in common is that they can’t really help Alex. Like a standup comic who semi-ironically suspects his microphone isn’t working, lonely Alex feels he isn’t being heard. But then he chances upon a comedy club and, to get in without paying the $15 cover charge, impulsively signs up to do five minutes. Finally, he winds up performing regular gigs without telling his wife, cheating on her with comedy itself, and doing material about their grisly sex life. Tess’s discovery of all this is spectacularly embarrassing.

And her reaction? Well, it’s not really believable, but Dern and Arnett are such good performers and work so sympathetically together that it comes off perfectly well in the moment. What might have been more plausible is that Alex, so far from being inspired by comedy to renew his relationship, sees the comedy value in its uproarious breakdown and creates more and more real-life opportunities to generate material, and Tess senses that she is becoming the butt of a joke of whose existence she has not yet uncovered.

Arnett has such a gentle face: handsome yet sensitive and wounded, the kind of face that you want to stroke sympathetically. He’s a good actor, and never anything other than committed, and it’s a relief in some ways to see a drama about comedians who aren’t supposed to be dark or malign. But I’d like to see a film about a comedian who, like Bishop, really does flower into being funny.