Begining The Sun Also Rises

Ok so I finally was able to track down a copy of The Sun Also rises. It was difficult but I found one at the Greenwood Library, which in fact I believe is a better copy because it was printed just a few years after the actual book was published! (this thing is ancient) Anyway, I began the book just a few days ago and I thought the way it began was very intersting. I thought that the main character was going to be Robert Cohn and the book would be told from the perspective of an all-knowing narrator. However, the narration switches over to Jake Barnes later on in the chapter. I was unsure of what significance this played but if i were to draw conclusions I would say that this technique was necessary to demonstrate the closeness of the narrator(Jake Barnes) to his friend Robert. I'm assuming Robert will have a huge impact on the story. Further more, by hearing from Jake what has happened through out Robert's life we learn how jake views certain topics and how robert's life relates to his own. Hopefully this is close to what the author was trying to get accross.