‘The Diary of a Teenage Girl’
Director:
Marielle Heller
Stars: Bel Powley, Alexander Skarsgard
Rating: R
3 (out of 5) Globes 

Traditionally we’re to believe — rightly, more or less — that age-inappropriate relationships are wrong. “The Diary of a Teenage Girl” entertains the notion that maybe it isn’t — sort of, to a point, if looked at a certain way. Based on a semi-autobiographical book by Phoebe Gloeckner that’s part graphic novel, part diary, it details the affair between a high schooler, Minnie (Bel Powley), and Monroe (Alexander Skarsgard), a strapping 30-something. It’s worse than that: he’s dating her mom, Charlotte (Kristen Wiig). It’s all very Bad Idea Jeans, and yet Monroe, as charmingly played by Skarsgard isn’t a slimy predator and, skeevy though it all is, they’re a more compatible couple than him and mom. It won’t last, but for a time — and off and on, as Monroe’s OK-ness with it seems to change by the minute — their love is a comfortable, rewarding oblivion like any other satisfying/doomed relationship.

To be honest, “Diary” is really only sympathetic because it’s all about Minnie. It’s not just a film about teen horniness; it’s a subjective beaming from the mind of a young woman dealing messily with messy feelings. This being from a graphic novel, and about an aspiring artist yet, the screen sporadically fills with animated doodles. It opens with its hero smiling ear to ear, crowing on the narration track, “I had sex today. Holy s—.” That the boning was with her mom’s boo is kind of alright, as it’s not only 1976 but 1976 in San Francisco. Having got a taste of it, she’s now gotta have it, and the rest of the film details her making what most people, even non-squares, would say are mistakes. She follows her hormones wherever they lead, sometimes down dark alleys, or at least to squalid drug dens or for instantly regrettable bathroom encounters.

RELATED: Bel Powley and Alexander Skarsgard on "The Diary of a Teenage Girl" and why he did drag

In its final stretch “Teenage Girl” comes close to being one of reactionary salvos that seems sex-positive only to ultimately punish its protagonist(s) for cutting loose. There’s a same-sex encounter that turns nasty, plus a final outcome for Monroe that comes close to being as cruelly regressive as “The Kids Are Alright” was towards Mark Ruffalo’s character. At least the latter can be defended as being true to its young character, who is bound to occasionally see things in stark, melodramatic fashion. That also explains why it can't escape certain coming-of-age and Sundance cliches. Here's the requisite shot of our young female star staring at herself starkers in a mirror; there's the lengthy monologue about What I Learned, plus an encouraging personal letter from Minnie’s favorite artist inspiring the very film you’re seeing.

This pat conclusion does, however, arrive after nearly two hours of emotional chaos, one that’s empathetic towards youthful pulchritude and mature pulchritude alike. It lives in the gray zone, not in the black or white, and even Charlotte — who would typically be a one-note shrew — wavers between struggling, temperamental single mom and cool single mom, trying to ignore that her daughter is making some of the same mistakes she likely did. As far as these things go, it's more raw than the kitchen sink "Fish Bowl" but nowhere near as out-there as the bonkers German sex saga "Wetlands." But it does capture the way that, especially as youths, we like to tear ourselves down, build anew, then start all over again. And it captures how adults do the same thing.

Follow Matt Prigge on Twitter @mattprigge