Director Judd Apatow (2012's "This Is 40") made an irrefutably wise decision when he hired Amy Schumer to write her very first, very own big-screen star vehicle. A brilliant—and brilliantly provocative—stand-up comedienne and the creator of Comedy Central's savagely smart "Inside Amy Schumer," she has a way of seeming sweet, likable and identifiable while speaking candidly and hilariously about sex, relationships, Hollywood double-standards, gender politics, and life in general. If Schumer's brand of humor is frequently blue, it also has purpose, and what she has to say about coming of age in her early thirties rings consistently true in "Trainwreck."

Amy Townsend (Amy Schumer) has grown up with dad Gordon's (Colin Quinn) not-so-sage motto ingrained in her head: monogamy isn't realistic. While younger sister Kim (Brie Larson) is now happily married to Tom (Mike Birbiglia) and takes joy in being stepmother to precocious 11-year-old Alister (Evan Brinkman), Amy has spent the entirety of her twenties in a haze of alcohol and one-night stands. If her romantic life has remained a stunted gray area, her career is starting to take off as she vies for the executive editor position at Manhattan-based men's magazine S'nuff. When her gloriously British, unapologetically unfiltered boss Dianna (Tilda Swinton) assigns her to write an article on sports doctor Aaron Conners (Bill Hader), the sports-averse Amy begrudgingly agrees, then finds herself genuinely enjoying spending time with the down-to-earth Aaron as more than just her writing subject. If Amy hopes to make what could be her first serious romantic relationship last, she will ultimately need to look inward and let go of the self-destructive patterns that have kept her from allowing love into her life.

To watch Amy Schumer in "Trainwreck" is to witness the breakthrough of an actress primed for superstardom. She has had bit parts in the past, as in 2012's "Seeking a Friend for the End of the World," but as Amy Townsend she is front and center for two hours, embodying a multifaceted protagonist beautiful in her messy complications and authentic in the unforced growth she experiences. That Schumer's screenplay comes from a sometimes intensely personal place is apparent in each frame, even when Apatow's direction is technically pretty standard-issue. The film's adherence to a three-act structure that pulls double-duty as a character study and a romantic comedy wouldn't normally lend itself to many surprises, but if the overall trajectory can be easily predicted, the way that Amy arrives at this place aches with an organic naturalism and fierce intelligence.

Never does Schumer or Apatow show contempt for their audience; they have made a movie with Universal Pictures of the likes that doesn't easily see the light of day in the studio system anymore. Enormously funny in spots but emotionally resounding, the picture's charm is in the astuteness of its perspective and the earnestness of Amy's arc from a fun-time gal whose commitments with the opposite sex typically last the span of one evening to a woman who discovers she yearns for something more but isn't convinced she deserves it—or should want it at all. Of course, it helps all the more that Amy Schumer herself is in the lead role. Hers is a hugely winning performance of demanding depth and range, and whether her character is playing a raucously uncomfortable game of Skeletons in the Closet at her sister's baby shower, navigating any number of awkward sexual encounters, struggling to understand what it means to be emotionally available with your significant other, or speaking from the heart about her beloved, if sometimes insensitive, father, Schumer sells her every moment and endears the viewer's rooting interest. Schumer refuses to sugarcoat Amy—she sees her in her best moments, and her worst—and this serves to only make her more relatable.

Beyond Schumer, the cast surrounding her get their own moments to stand out. As Aaron, Bill Hader (2014's "The Skeleton Twins") is perhaps not the first person one would think of to play the central love interest, and yet he is perfect for his role as a sports doctor with a penchant for Billy Joel's "Uptown Girl" and a genuine fondness for Amy. Aaron is written as a mature adult who isn't just going to coldly walk out on a person he has grown to care about, and Hader's best moments are the ones where he shows her that relationships are sometimes difficult, but part of loving someone is the act of working through disagreements and moving on from them. As Amy's more straight-laced, put-together sister Kim, Brie Larson (2012's "21 Jump Street") shares a warm, but not entirely uncontentious, sibling chemistry with Schumer, the two of them dealing with the financial strain and guilt of putting their MS-afflicted dad in an assisted living facility. Colin Quinn (2013's "Grown Ups 2") plays dad Gordon with a nice low-key grace, exhibiting an obvious affection for his girls even when he is being difficult and speaking his mind. Vanessa Bayer (TV's "Saturday Night Live") is dynamite as Amy's easily unnerved friend and colleague Nikki, earning numerous big laughs with her sneakily distinct comic timing. If there is one best-kept secret finally revealed by "Trainwreck," it is that Tilda Swinton (2014's "Snowpiercer") has been an untapped comedic force for far too long. Totally unrecognizable as the super-glam, unforgivingly honest editor-in-chief Dianna, Swinton has never had a part like this; very nearly every one of her magnificently biting line deliveries threatens to bring down the house.

At 125 minutes, "Trainwreck" continues Judd Apatow's streak as a filmmaker who never met a two-hour-plus running time he didn't like. As per usual, the editing could use some tightening, beginning with NBA player LeBron James' too-sizable role portraying himself (and Aaron's go-to confidante). James is natural enough on screen—much more so than a lot of athletes who dip their toes into acting—but many of his scenes slow down the pacing and aren't half as amusing as they seem to think they are (much more successful, for what it's worth, is WWE fighter John Cena's inspired turn as Amy's lunkheaded would-be boyfriend Steven). A third-act intervention Aaron receives involving Matthew Broderick and TV sports commentators also falls flat, and could have easily been excised. These digressions, however, are minor specks in the shadow of all that the film gets right. The blending of humor with pathos, and the ease with which it marries these two tones, is one of the film's many notable achievements. An elaborately choreographed dance sequence near the end brings it all together, an exuberant declaration of love that earns the right to be silly and sweet in equal measure. "Trainwreck" is anything but a throwaway vanity project; it has been lovingly conceived and structured as it tells a complete, dramatically resonant story about a woman who stumbles, makes mistakes, and comes out the other side a stronger and wiser person with a newfound understanding of all the things that are most important to her. The glorious ode to "Working Girl" in the movie's opening minutes doesn't hurt, either. This is a shrewdly satisfying, blessedly adult-minded pleasure with suspected high replay value, and in Amy Schumer is a uniquely incisive voice that the world of comedy needs. With any luck, a new film career has just been born.