A Game of Thrones Theme of Memory and the Past

There's a famous quote from William Faulkner: "The past is never dead. It's not even past." That's a pretty good summary of how the past works in A Game of Thrones. It's like throwing a rock into a pond. Let's call that rock "Robert's rebellion against the Targaryens": the rock may be in the pond already, but the ripples are still going out. And it's not just recent history that has ripples – some ancient, ancient history seems to be returning, too (the return of the Others in the north and the re-birth of dragons in the east). In A Game of Thrones, the past is rapidly catching up with the present.

1. Who do you trust when it comes to history and memory? Can we trust Old Nan, even though her memory isn't so great (she doesn't even know how old she is, for crying out loud)? Is there any way to know the truth about the past?
2. Dany gets her history of the Seven Kingdoms from Viserys (at least, until Jorah gives her a book as a wedding present). How does Viserys' version of history differ from the history we see elsewhere? (And do we ever hear again about that little book of history?)
3. Not a lot of characters in this book can read. (They didn't have Shmoop back then.) How does this lack of literacy affect the way that history is remembered and passed on?
4. How does George R.R. Martin build up the history of this imaginary world? Were you interested in the discussions of history or did they interrupt the exciting present? How would the book be different without all this discussion of the past?