In Cryptonomicon, Neal Stephenson employs an effective tactic for shifting perspective from third-person to first-person narrative. As he has a character observe the world, he will shift from description to explanation. He uses this primarily with the Waterhouse characters, mathematicians whom I suspect most Stephenson fans readily identify with. Typically, a description of a pattern in the environment shifts to an exploration into the ramifications of that pattern, particularly how it might illuminate some underlying influence. In this way he not only shifts perspective, but also ties the experiences of characters in different threads together.
I am so drawn in by this, that I find myself shifting towards similar trains of thought myself. More readily than usual, that is. While flying today, I was reading one of these diversions into "Van Eck phreaking" and noting the obvious correlation to an earlier treatment of the footfalls of pedestrians in London (and references to sonar location, and of course copious computer science and cryptography discussions. Looking out the window, I absent-mindedly began trying to discern patterns in the natural paths of streams and artificial paths of highways etched through the landscape.
You gotta love a book that puts you into the mind of a character so completely that it affects your own conscious thought.