It basically voices the first parts and if you are interested there is the rest waiting for you, and that's generally what the whole plot is like. That's actually a really good idea because the developers get away with less recorded voice work and save space on the game but it also isn't a pure 'read piles of text for hours to follow the plot' either.
When I stopped to read messages in my PDA and other things it was nice, and I liked the voiced dialogs (only the first few paragraphs or each quest are voiced but it helps get you into it to start). There is a problem with this, however, as the game really doesn't do a good job of pushing the story on you and I found myself not really caring and only having a vague idea of the plot for most of the game. Stalker has a relatively nice plot that threads throughout the game, it's not going to win any awards or anything but it does more than just sit there to hold the game together and if you want to get really into it you can get lost in a bit more depth. May read it myself later, either way here it is: 'read piles of text for hours to follow the plot'
I haven't even re-read it I just think it needs a better home than google sites :S.
Found this and forgot I'd even wrote it, it's just a review after finishing stalker that I apparently needed to write.