I loved the film's opening scene, which sees Jackie Kennedy padding around the White House glumly in slow motion with these wonderful curtains of sound wafting around her, all stretched and dissonant, reminiscent of the opening of There Will Be Blood. And Nathalie Portman is immediately extremely impressive, strangely invisible in the lead role.
Although she's too good-looking to fool anyone in a line-up, it's an eerie impression, and she has that sleepy, almost-spooky, lugubrious ASMR monotone down pat. Jackie Kennedy always sounded rather like Marilyn Monroe might have, in her final moments of consciousness.
The film flashes back to key episodes in Jackie's life as the President's wife, returning each time to an interview she is conducting a week after her husband's assassination. As the interviewer continues to probe his subject, who just happened to be the most famous woman on the planet at the time, the film becomes increasingly intrusive. Predictably, we revisit the moment of JFK's death again and again, seeing a little bit more of his brain each time. We also see more and more of Jackie dealing with his death.