Better than most of the movies in the genre, especially at portraying the truth about inpatient rehab centers. In truth, especially in places where many of the "patients" are only there to avoid prison--for a while--the reality of predatory inmate/patients who prey upon vulnerable ones is inescapable, and the behavior is, if not rewarded, certainly not punished. That was one of the places where I had to suspecd my disbelief, as a young man with no legal problems and wealthy parents would be unlikely to spend his first rehab experience in a rehab that was basically a substitute for jail. He'd be much likelier to be in the "Clean and Sober" or "When a Man Loves a Woman" nice clean treatment centers with other patients who were nice ladies and gentlemen. Maybe his folks were just cheap.
I wasn't real sure about the ending. Was it reality or was it a dream? Since they showed the flashbacks of him with the one girl he was with when he overdosed the first time, and going into that dream world, I thought perhaps it was another dream sequence. If it was supposed to be reality, however, I again felt I had to suspend my disbelief. Generally people who have just come out of rehab are able to hold out a little longer. But, the truth is, that if they use, especially drugs like heroin or methadone, their tolerance will have been reduced by a month of two clean. If they use the same amount--and he'd overdosed once on this drug, whatever it was (probably supposed to be heroin) before he went to treatment--often they overdose on an amount they were able to do before.
A couple of other questions: What were he and his friend making in his friend's house? The only drugs that people, even those who know a little chemistry, make in their kitchens are crystal methamphetamine and a few designer drugs. Heroin and cocaine come from plants. I suppose it's possible they could have been purifying either, or processing black tar heroin into white heroin. I've never heard of anyone doing that in a home lab, though, so my guess is crystal meth. There's also fentanyl powder, but making black market fentanyl, which there is a lot of these days. However, nobody makes that in a home lab either. Last but not least, what did Molly overdose on when she shot up on the roof? It looked like a bottle of drain cleaner, but I can't imagine anyone wanting to die badly enough to shoot up drain cleaner. Do you know how painful that would be?
Altogether, a worthy effort, but with just a little bit more attention to detail, it could have been outstanding.