This semi-abstract portrait of Jacqueline Kennedy during the immediate aftermath of her husband's assassination is more a showcase for Natalie Portman than anything else. However, history buffs – specifically, Kennedy fetishists – will surely be drawn in.

Chilean director Larraín likes taking risks with format: his breakthrough feature No, set in the late '80s, was shot on '80s-era video. This time he and his DP Stéphane Fontaine shot on super 16mm, making Jackie look like it might have been made in the early '60s. (Like No, Jackie employs a squarish aspect ratio.) Sometimes it's strangely flat, sometimes it's gorgeous and etherial.

The story's framing device, in which Jackie, weeks after the assassination, is interviewed by an unnamed reporter (Billy Crudup) and flashes back to the week of November 22, is a tad clunky. Screenwriter Noah Oppenheim, whose only previous credits are on YA dystopian flicks The Maze Runner and Allegiant, is the weak link here. Jackie often bogs down in self-reflective, self-pitying dialogue. I found myself wishing there could be more of a story besides Jackie flipping back and forth on Kennedy's funeral arrangements, hoping to ensure his place in American history before she gets booted out of the White House.

That said, there's a lot about Jackie that I like. First and foremost, Portman is terrific. This isn't a vanity project, this is serious actor craft. Her breathy patrician dialect will turn off some viewers, but I found it helped her transform from Hollywood star into the inscrutable Mrs. Kennedy – and it also took me back in time. (A period picture in which the actors speak in modern cadences is a pet peeve of mine, so this was welcome.) The rest of the cast suffers a little from spot-the-familiar-face – there's Peter Sarsgaard as RFK, Greta Gerwig as Jackie's Social Secretary Nancy Tuckerman, John Hurt as a fictitious priest – but they're all solid. The film's secret MVP may be composer Mica Levi. She knocked my socks off with her infectiously creepy first score, for Under the Skin. This time she employs atonality to emphasize the surreality of the post-assassination days, softening it here and there with warmer, haunting themes. She's a real talent.

That score is bound to polarize audiences, just like Portman's dialect, Larraín's noncontinuous if stunningly composed shots, which owe a little to Terrence Malick, and the film itself. As for me, I admit that after a while I found Jackie somewhat tedious: Oppenheim's navel-gazing dialogue ultimately runs out of places to go. Still, as a dreamlike portrait of one of the most intriguing Americans of the 20th century, I recommend the film.