On Monday night, Judd Apatow and Amy Schumer unveiled the fruits of their labor at SXSW to a packed house at the Paramount Theater with a “work in progress” screening of Trainwreck. I’m not entirely sure what they meant by “work in progress” because it seems like they have a fully formed (and very, very good) product on their hands already. After visiting the set this past summer, I had little doubt that the film would be anything short of hilarious. The result was even funnier–and sweeter–than I had imagined, a fact corroborated by the constant, uproarious laughter of the crowd throughout the two-hour screening.

Ever since The 40 Year Old Virgin, Apatow’s calling-card has been riff-heavy, lewd, but ultimately heartening stories about emotionally stunted manchildren learning to grow up. Moreover, they were usually films that Apatow wrote himself, extensions of his own experience and a way for him to come to terms with his own adulthood. This time around, however, Amy Schumer handled scriptwriting duties, and the result is acerbic, charming, heartfelt, and searing all at the same time. With her rapier wit and pitch perfect delivery, Schumer uses Trainwreck as a means to shine a light on the ways in which we sabotage our own chances at happiness, and how we can pick ourselves up again.

In addition to writing and producing, Schumer stars in the film too. Her character, also named Amy, is a writer for a sleazy men’s interest magazine called S’NUFF, an outlet where stories like “The Ugliest Celebrity Children Under 6” and “You Call These Tits?” are par for the course. Though she is more than a capable writer, Amy is merely drifting through life in a haze of hangovers, marijuana smoke, and ill-remembered sexual conquests. Speaking of the sexual conquests, they are a point of pride for Amy, who has hard and fast rules for dating men–or rather, not dating them–all of which basically boil down to “never let them get too close” and “don’t get too attached.” All of this stems from her father (Colin Quinn), who drilled the maxim that “monogamy is unrealistic” into his two young daughters in order to explain that he and his wife were getting divorced. And you thought your dad was embarrassing.

Amy’s sister, Kim (Brie Larson), has managed to outgrow her father’s words of “wisdom”, and is happily married to a loving husband, Tom (Mike Birbiglia), and his precocious child from a previous marriage, Allister (Evan Brinkman). Yet, for Amy, marriage is emotional stasis, which is tantamount to death, so she continues to run from commitment–and pass judgment on others who don’t follow suit. Case in point, she can’t bring herself to be exclusive with her on-again, off-again “boyfriend” (hilariously played by John Cena), who wants to make an honest woman out of her. She seems to be so intent on self-destruction that she’s willing to undermine every budding relationship she has just to make sure she doesn’t make any perceived mistakes that monogamous couples are doomed to repeat.

Assigned to write a profile of a sports doctor named Aaron (Bill Hader), a surgeon who specializes in rehabilitating injured athletes, Amy is resistant because she admittedly hates sports. However, when she sits down to meet Aaron for the first time, there is an immediate, undeniable chemistry between the two. Not only does is Aaron dryly witty and endearing, but he performs charity work with Doctors Without Borders (or “Doctors With Borders” as Amy calls them) and is about to perform a revolutionary knee surgery on injured New York Knicks player Amar’e Stoudemire. Oh, and his best friend just so happens to be LeBron James. Yes, that LeBron James.

One thing leads to another, and Amy and Nick wind up sleeping together after knowing one another for less than 24 hours. To Amy, this means that’s the end of the line; they’re done. Naturally, she is surprised and more than a little suspicious when Aaron calls her the next day wanting to see her again. She’s even more surprised when they wind up in a full-fledged relationship together, something she never saw coming in a million years.

What follows is essentially a rom-com with roles inverted in clever ways. The best example of this is LeBron James, who may well be the breakthrough performance in a film full of breakthrough performances. In a typical Apatow film, Hader would be playing the romantic female lead, the unwitting or seemingly unattainable object of desire for the male lead. By this logic, LeBron, playing himself, serves as the best friend with a shoulder to lean on and a piece of handy advice always at the ready. It’s a role that LeBron steps into fearlessly, committing 100 percent, and creates an endearingly goofy character who is fiercely protective of his friend Aaron, insistent about always splitting the bill, and surprisingly into period dramas like Downton Abbey.

Though the script itself is well constructed, the supporting cast is largely what makes the film such a pleasure to watch. A murderer’s row of funny people parade through the story, including Tilda Swinton, Marisa Tomei, Ezra Miller, Vanessa Bayer, Randall Park, Dave Attell, Jon Glaser, Leslie Jones, Nikki Glaser, and many, many more. The film is at its best when it allows Schumer’s comic sensibility to channel through someone who you might not regard as being traditionally funny, like John Cena. His attempts at dirty talk and tough-guy retorts will have you crying with laughter. The whole film is packed to the gills with tremendous talent, which Apatow has weaponized to execute Schumer’s vision with laser accuracy.

It’s not all fun and games, though. Schumer explores the darker side of her character through an alternately sweet and devastating storyline about her ongoing relationship with her father, who has multiple sclerosis. Dealing with the realities of having to place a parent in an assisted living facility–and pay for it–and watching someone you love wither away before you is kind of stark material for what is otherwise a comedy, but it lends pathos to the film and a real sense of depth to Amy and her sister Kim. This is some heady material that proves Schumer’s merits as an actress, too. Of course, it helps that she is playing against Brie Larson, who turns in a typically excellent performance.

Though it starts to drag a little bit in the final third and some of the narrative conceits seem a bit by the numbers, Trainwreck‘s outsized charisma, raw honesty, and adroit direction make you forgive the film for its sins. Schumer’s self deprecating, razor sharp wit is on full display here, and this film is her mic drop. Apatow and Schumer’s comic sensibilities are in creative lockstep, and it makes for a terrific product. Woody Allen had his New York (wickedly referenced in a mid-film montage), but I want to see more of Schumer’s. Especially if that means more LeBron James.

Rating: 4.5 out of 5 burritos

Trainwreck is in theaters on July 17, 2015.