A Process Of Elimination

I think going to the Milton Maize Maze after watching A Scanner Darkly rather than before would have been much more disturbing. For all that I've read the book a couple of times I think it's worth watching twice, to see how it stands on its own rather than understanding it through familiarity with the source material. And I would say that the answer is that it does it well.

(Also it's long enough since I've read the book that the film is forced to stand alone now...)

Total Recall plays a bit with questions of reality, but Arnie's never really fooled for long ("consider this a divorce"). Scanner does a much better job: it's much clearer to the viewer that the characters are having real trouble with distinguishing reality from the effects of the drugs they're taking. Freck and Barris are obviously not the sharpest tools in the box, but Arctor's hallucinations are shown as coherent and inescapable; his personal experience of reality has unambiguously shifted.