What makes Tarkovsky interesting is the very form of his films. Tarkovsky uses as this material element of pre-narrative density, time itself. All of a sudden we are made to feel this inertia, drabness of time. Time is not just a neutral, light medium within which things happen. We feel the density of time itself. Things that we see are more markers of time. He treats even humans in this way. If we look at the unique face of Stalker himself, it's a face of somebody exposed to too much radiation and, as it were, rotting, falling apart alive. It is this disintegration of the very material texture of reality which provides the spiritual depth. Tarkovskian subjects, when they pray, they don't look up, they look down. They even sometimes, as in Stalker, put their head directly onto the earth. Here, I think, Tarkovsky affects us at a level which is much deeper, much more crucial for our experience than all the standard, spiritual motives of elevating ourselves above material reality and so on. There is nothing specific about the zone. It's purely a place where a certain limit is set. You set a limit, you put a certain zone off-limit, and although things remain exactly the way they were, it's perceived as another place. Precisely as the place onto which you can project your beliefs, your fears, things from your inner space. In other words, the zone is ultimately the very whiteness of the cinematic screen.
Slavoj Zizek's The Pevert's Guide to Cinema (2006)