All of Philip K. Dick's writings pre-date cyberpunk as a genre but were very influential in the creation of cyberpunk. So he represents a proto-cyberpunk period in time. Also, most of his books are about drug use and questioning reality.
When his books are only used as the foundation of a movie, amazing things can happen (Blade Runner, Minority Report, Total Recall). But when you create a faithful adaptation of his works it always ends up... kinda weird. A Scanner Darkly follows its source material very closely. So even though the movie was made in 2006, it really represents a proto-cyberpunk point in time. And it's all about taking drugs and questioning reality.
The movie has big-name actors (Keanu Reeves, Robert Downey Jr, Woody Harrelson, Winona Ryder) but the majority of the movie is just a bunch of junkies sitting around their house being weird. The rotoscoping animation style is really cool (and used to great effect here) but it isn't enough to get me to care about the story. I don't know, I guess I'd call this movie interesting but I'm not sure if it's good.
Here's a trailer. I don't think it's streaming anywhere though.
I think maybe it wasn't a great choice to try to make it a faithful adaptation for a couple reasons, the biggest one is pacing. It throws a lot at you very quickly and it's pretty difficult to follow what is going on, with the book there is obviously more time to mull it over. Another is how much is conveyed through wordplay and the way things are phrased.
One thing I like about it is how it explores the themes of the difficulty of trusting others when it's impossible to know what reality is, the difficulty of caring for or not betraying them, and how that can also be extended to yourself.