Just in time for the holiday season, here is a giant pile of shiny gift-wrapped garbage titled “Vox Lux.”

Open and proceed at your own risk.

The sophomore effort from the talented writer-director Brady Corbet (following the excellent “The Childhood of a Leader” from 2015) shows flashes of provocative promise in the first half hour or so, but ultimately devolves into a screeching, empty, exploitative cinematic cacophony about as entertaining and insightful as multiple sets of nails scratching across multiple blackboards until we’re begging for mercy.

Pretentious deadpan absurdity abounds, starting with the instantly identifiable voice of Willem Dafoe as the unseen narrator, who delivers his lines as if reading a modern-day fairy tale about a girl who becomes a star.

And indeed, “Vox Lux” IS about a girl who becomes a star — but one of the major problems with the film is the girl is at least interesting and sympathetic while the grown-up version is a hysterical, egomaniacal, deeply addled narcissist and one of the most off-putting characters to appear in any film of 2018.

Making matters so much worse: the brilliant and beloved and greatly decorated actress playing that grown-up star delivers arguably the worst performance of her storied career.

More on that in a moment, but first let’s sift through the early stages of “Vox Lux,” which manages to weave in (and exploit) not one but TWO fictional mass shootings as well as the horrors of 9/11 into a bold and wildly ambitious Pop Culture Statement that ultimately has almost nothing of value to say.

I mean, when a film is broken into “acts” and Act 1 is titled “Genesis,” it’s almost spoiling for a fight, almost daring us to fold our arms in skepticism.

Credit where its due: That opening segment, which begins in 1999 and continues through the first couple of years of the 21st century, is actually a darkly effective, borderline surreal passage — making the latter two-thirds of the film all the more disappointing.

Raffey Cassidy gives the best performance of the film as 13-year-old Celeste Montgomery, a sensitive and gifted girl who suffers near-fatal injuries in a Columbine-like shooting at her school.

While hospitalized, Celeste and her older sister Elle (Stacy Martin, also quite good), compose a song about the tragedy — and when Celeste performs a beautiful, soulful rendition of the song at a memorial service with the news cameras rolling, she attracts the attention of a grizzled, veteran music act manager (Jude Law), who sets the wheels in motion to turn the song into a worldwide anthem and turn Celeste into a spunky, sexy little pop star.

Reminder: Celeste is a child. Any illusions we have about The Manager (as he’s billed in the credits) actually caring about Celeste and her sister as he takes them on the road and into the studio are shattered quickly when we see how eagerly he feeds the machine that forces both girls to grow up far too quickly.

Cut to 2017 and Act II, titled “Regenesis,” with Natalie Portman playing the 31-year-old Celeste, who is now a hugely successful, often controversial, tabloid-fodder, Madonna-esque international pop star with a teenage daughter.

In a terrible and distracting piece of casting, Raffey Cassidy, who played young Celeste, is now playing the teenage daughter — but it hardly seems like a dual role, given the daughter looks and sounds almost exactly the same as young Celeste. And while daughters often DO look and sound like mini-versions of their mothers, in this case it comes across as an unnecessary stunt.

Jude Law is still around as the Manager and Stacy Martin is still with us as older sister Elle, though neither looks 18 years older than he or she did in Act 1. Elle has been raising Celeste’s daughter because Celeste has been preoccupied with touring the world, recording hit albums and video-friendly singles, racking up a DUI while running someone over, indulging in multiple addictions and generally making one horrible decision after another while behaving like a spoiled brat virtually every second she’s not onstage.

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Natalie Portman is one of our finest actresses, but her over-the-top performance is a howler for the ages. Whether Celeste is stumbling about on a drug- and booze-soaked bender, cruelly berating a clueless restaurant manager who dares ask to take a photo with her or rambling on in me-me-me fashion at a hastily called press conference after overseas terrorists don masks fashioned after a “classic” Celeste video before shooting up a beach, Portman portrays her as a vapid, loud, charmless vessel.

Yes, we understand this woman endured an unspeakable tragedy as a child and was exploited throughout her youth, but as written by Corbet and interpreted by Portman, Celeste is an irredeemable, shrill, often cruel and nearly empty shell.

“Vox Lux” closes out on a series of sour notes, in the form of a splashy, seemingly endless concert montage, with Portman/Celeste performing a bunch of catchy, arena-friendly but almost instantly forgettable pop tunes (written by Sia).

Through it all, Natalie Portman is a gamer, but in the case of this neon nightmare of a film, it was Game Over long before she hit the concert stage.

‘Vox Lux’

Neon presents a film written and directed by Brady Corbet. Rated R (for language, some strong violence, and drug content). Running time: 112 minutes. Opens Friday at local theaters.