Joaquin Villalobos’s review published on Letterboxd :
In a film about heroin addiction, homelessness, and the pervasive hustle informing them on any given day, it’s startling that what’s foregrounded from the start is the ugly scheme of an all-consuming co-dependency. Instead of the drug use itself, we get “love”—or rather, the hellish loop of one-upmanship—between two junkies named Ilya (played with such veracity by Caleb Landry Jones that you’d never guess he’s the sole professional actor) and Harley. She’s based on and played by Arielle Holmes, the addict who’s walked in those shoes at the age of nineteen just a couple years prior. It’s her first performance, and from a screenplay adapted directly from the book a directing team commissioned her to write.
Her Mad Love in New York City came to be Heaven Knows What so fast, a whirlwind of their chance meeting in a subway station, learning her powerful story, and encouraging her to get it down on paper for the sake of playing herself (and to focus away from the drugs) in a small film about her present-day life. That urgency to capture a time, place, and emotional reality to a drug addict’s ever-shifting intentions lends the film a sharp precariousness, an unease that the next turn will bring the worst to either Harley and her exploits or the film’s sustainment of a striking verisimilitude. Brothers Ben and Joshua Safdie went undeterred by the imagined line dividing “realism” from fiction that so many young directors get hung up on never crossing. They took huge and admirable risks with this production, melding the best effect from both camps and gambling with the odds any of their non-professional cast could disappear without warning, whether for a fix or at the hands of the law. But they somehow knew Holmes would deliver on her promise, and it’s her core involvement and astounding performance I don’t hesitate to credit with the majority of the film’s authorship.
Within the tense opening minutes, she goes from Ilya’s tight, rapturous embrace to the emergency room with a wrist she slashed using a fresh razor blade, all to prove her willingness to die for Ilya; but really, it proves her helplessness in the face of his wicked manipulations. It’s a terrifying scene, both in the hard-nosed approach with which it handles an attempted suicide and how quickly their relationship swings from locking lips on the dirty concrete to her blood spilling all over it. The Safdies don’t give us a reprieve from that point forward, not even in the treatment center she’s immediately taken to over the film’s opening credits within a single, unshowy tracking shot, knowing there’s enough chaos in the frame—Harley defying doctor’s orders, screaming patients picking fights, and nurses having to act as security guards—to corner us amidst her clamor. It’s an interior space the Safdies continue externalizing through sound design in a lulling mix of eerie, skin-crawling blips and electronic covers of classical music. Debussy’s “Clair de lune” becomes the drab, diffused winter of New York City, seemingly mocking the romanticizing of addiction in most of Heaven Knows What’s predecessors.