Here's one way Booksmart diverges from previous coming-of-age buddy flicks: When the relationship of best friends Molly (Beanie Feldstein) and Amy (Kaitlyn Dever) reaches a crucial juncture, the soundtrack cues up "Unchained Melody." In a movie about male BFFs, there's no way that über-romantic song wouldn't be used ironically. In Booksmart, it couldn't feel more sincere.

While the screenplay has already established their relationship as platonic (Molly is het, Amy gay), these two adore each other, and their affection is infectious. It contributes to the festive mood of this party-centric high school comedy, the first feature directed by actress Olivia Wilde.

Booksmart doesn't reinvent the wheel: Its influences are legion, from John Hughes to Romy and Michele's High School Reunion to Judd Apatow and Diablo Cody. But it updates its subgenre for the selfie generation while embracing the reality that, in 2019, there's no longer a clear line (if there ever was) between the nerds and the in-crowd.

For class president Molly, who's headed to Yale University, her smarts define her identity. Headstrong, loud and more than a little obnoxious, she derides her fellow seniors as slackers — until she overhears them calling her a "butter personality." When she realizes that her disdained peers managed to party and study, Molly's world collapses. Desperate to "prove to them that we are fun," she persuades Amy to spend the night before graduation at an unsupervised house party.

That's where the trouble starts. While the girls' phones show them the party's high jinks in real time, its physical location remains elusive. They spend much of the movie chasing their goal through ever more surreal distractions, from an obscenely lavish shipboard graduation party to a drama geek's murder-mystery dinner.

In its quest structure and escalating absurdity, Booksmart recalls the Apatow-produced Superbad, but its comedy chemistry formulas are its own. Feldstein (Saoirse Ronan's sidekick in Lady Bird) and Dever (who played a hardscrabble teen pot grower on "Justified") are two performers who've deserved a better showcase for a while. One flinty and the other flighty, both frank and raunchy and equipped with death glares to die for, they're great together.

Booksmart has memorable supporting players, too, including older-generation comedians such as Lisa Kudrow and Jason Sudeikis playing painfully uncool adults (a tradition in these movies). But the standout is Billie Lourd as a rich, eccentric burnout who somehow crops up everywhere Molly and Amy go. She suggests Kate Hudson's Penny Lane after a few very long, strange trips, and, in one of the movie's running jokes, she, too, has managed to secure admission to the Ivy League.

Some of these supporting characters could have used firmer grounding early on; we may not feel like we know them when they abruptly take on key roles in the plot. But that flaw is a symptom of Wilde's tight focus on Molly and Amy's relationship, a choice it's tough to fault.

While acting on romantic crushes is part of the duo's mission to come of age in a single night, their pursuit of booty never veers off into fantasy fulfillment, and it never overshadows their bond. It's easy for a movie to spout platitudes about female solidarity, but these two feel like the real deal.

Booksmart isn't about Amy and Molly growing out of their friendship as they discover a world beyond the library. It's about their stepping away from books and screens long enough to interact with their peers as people rather than social-media-molded "brands," and that's a smart message indeed.