Other than Harry Potter and LoTR, GoT was my first real foray into the fantasy genre. I'd previously assumed that books of this sort were largely for the teenage reader, so was pleasantly surprised that this isn't the case.
The manipulation of history, as you describe it P, doesn't bother me at all and I rather enjoyed the parallels. It isn't really any different from any other fiction which has been loosely based on some historical era in that respect.
What do they do for history? The books are sold as fantasy, not as historical fiction or non fiction and I think most people are prefectly capable of keeping the two seperate. Unless one is Phillipa Gregory, that is
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PS edit. I think bttdp has a GoT thread going somewhere around here also.