Gisli Sursson's Saga

Of the sagas we have read thus far, this was my least favorite. It was very long and confusing. I noticed that throughout the sagas, and in the first few chapters especially, many characters were introduced. As I read this, I really began to ponder how people remembered all the names and characters. I know for certain that if I was telling this tale, I would have cut out immense portions of the saga. If I was sitting around a fire listening to this story, I doubt I would care about all the names. And in this aspect, this saga differs from others. It's more of a recounting of people than an actual story. How many of the characters in this story were actual people? As this story was passed down through generations, did it change any?