It's a slow build--don't give up on it too early
If I hadn't previously seen The Parallax View by the same filmmaker and been so blown away by that, I might not have stuck with this one as it takes a little time to sink its teeth in you. I ended up watching it over three days and four or five different sessions; but I found it quite rewarding that way. Someone on another thread said it was like reading a book, and books are often enjoyed in segments, so I would recommend trying that if you find your attention wandering a bit at the beginning.
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See a list of my favourite films here: http://www.flickchart.com/slackerinc