Lars von Trier’s Nymphomaniac isn’t really about sex—or at least the first volume isn’t. Nymphomaniac: Volume I is undeniably sexually explicit, with a prurient hook that has a woman named Joe (played by Charlotte Gainsbourg as an adult, and Stacy Martin as a teenager) recounting her complete sexual history to a curious academic named Seligman (Stellan Skarsgård) after he finds her bruised, bloodied, and unconscious in the street. But Joe’s extended, illustrated anecdotes of how she learned to control men through sex isn’t all there is to Nymphomaniac. The movie isn’t a monologue. It’s a conversation between a woman trying to explain herself as dispassionately as possible and the eager intellectual who keeps interrupting her with questions and analogies, trying to fit everything she says into a form he can analyze—and thus understand. The whole first half of Nymphomaniac is like a passive-aggressive argument between an artist and a critic.

Nymphomaniac’s title is printed onscreen as Nymph()maniac, which is apt for two reasons: because the parentheses recall female genitalia, and because the symbol breaks the title in half, leaving two distinct words. Whether “maniac” properly describes the second volume of Nymphomaniac remains to be seen—although a semi-comic “next time on Nymphomaniac” montage that plays during the closing credits seems to imply it does—but “nymph” is the right word for volume one. Divided into five chapters (the second volume will add three more), Nymphomaniac: Volume I covers Joe’s story from childhood through college and into young adulthood, and organizes her life through her prodigious sexual experiences. She loses her virginity to a local stud named Jerôme (Shia LaBeouf), who continues to pop up over the years and bewitch her; she and a friend have a contest to see which of them can have sex with the most men during a train ride; she forms a club at university for women who only want sex, not boyfriends; she draws up a complicated rotation of regular lovers after she graduates; and so on. In Joe’s eyes, at least, sex is at the center of who she is—or at least explains who she becomes, in the second half of her story.

Though Joe’s narrative is repetitive, Nymphomaniac: Volume I is fairly eclectic. Von Trier takes a variety of approaches across the chapters, switching up the look of the image and the pace of Joe’s anecdotes. Sometimes the film is like a slapstick, quasi-pornographic montage, as Joe recites a litany of her sexual partners. But then Nymphomaniac slows down for a harrowing black-and-white sequence where Joe visits her dying, delirious father (Christian Slater) in the hospital. Then it shifts gears again for a hilarious, jaw-dropping scene in which the wife of one of Joe’s lovers (Uma Thurman) drops by Joe’s apartment with her children, to show them the “whoring bed.” And then there are all of Seligman’s interjections, which serve as entertaining mini-lectures on fishing and music theory.

Not all of these segments work equally well. Some drag on, and some seem overly facile in their depiction of sexual desire. Also, it’s impossible to weigh the worth of Nymphomaniac: Volume I without seeing Volume II, which has the potential to change the context of everything that’s come before. (The first film ends on something of a cliffhanger.) But so far, Nymphomaniac looks like a major work from a major director: a compendium of all von Trier’s career-long preoccupations with gender roles, authoritarianism, religion, obsessive behavior, and lust.

It’s a tricky film, too. For example, is it a coincidence that Joe’s list of rules for her fellow sex-fiends in college resembles von Trier’s Dogme 95 movement—and are just as hard for their adherents to follow? Could Nymphomaniac really be von Trier’s story—not about his sex drive, but about his art? Or does even asking these questions turn viewers into Seligman, wanting to impose their own meaning before seeing how it all ends? Whatever comes next with Nymphomaniac, any film that can challenge and provoke this way—sometimes playfully, sometimes shockingly—is a film worth following to whatever dark places it may be about to go.

Nymphomaniac: Volume II is reviewed here.