I can't remember the name of the book, or what exactly the words were, but I can remember the image that the first few lines left me with still. It was about the V that the trees made along the sides of a very long and straight river. I believe it was a Jack London book, not sure though. But the words were so powerful that I remembered the image for a long time. (I was probably 10 when reading it). So in my opinion, the first few lines are exceptionally important. Dialyn is right though, the words need to fit the story.