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Change, like winter, is coming to Westeros. Indeed, it's already arrived.

Ever since the very first season of "Game of Thrones," differences between the HBO series and George R.R. Martin's "A Song of Ice and Fire" novels have existed — but with each passing season, those changes have grown, from wholesale omissions of characters and story lines (Lady Stoneheart, anyone?) to brand-new characters and stories revealed only on the show.

The differences between the books and the show are set to expand even further with the show's upcoming fifth season. Photos from the set have revealed major alterations to multiple prominent characters, and there are rumors of other stories from the books not making the cut.

"I've been saying for four or five years that we're heading in that direction," Martin told MTV earlier this week, while promoting "The World of Ice and Fire" in New York City. "I said that as early as my season one interviews: It's the butterfly effect."

"Sometimes you make a small change in season one, and it requires a bigger change in season two, and a bigger change in season three, and it snowballs," he continued. "I think to some extent, that's what's happening here."

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But does that explain the inclusion of something like the final scene of season four's "Oathkeeper," in which viewers saw the White Walkers' base of operations for the first time? The scene does not exist in the books — not yet, at least — and seems to mark either a major change from the "Ice and Fire" novels, or an early look at what Martin has planned but not yet published.

"When you see a scene that's not in the books, it can actually be one of three different things," said Martin. "It could be a scene that could have been in the books but I didn't have a viewpoint character there, like the scene between Bronn and the Hound in the 'Blackwater' episode of season two; there's no reason it couldn't have happened in the books, except neither of those guys are viewpoint characters."

"Then there are the scenes that David and Dan have gotten to before the books have gotten to them," he continued. "They will be in the books, but David and Dan, knowing what's coming, have moved it up a little."

"And then there are scenes that are in the show that will never be in the books, past or present, and could not be in the books, because of the butterfly effect."

Of those three options, it's the second one that proves most problematic for some book readers. Part of the joy of "Game of Thrones" for book-first fans is seeing non-viewpoint characters in their own scenes, ala Bronn and the Hound. The butterfly effect that Martin describes is understandable from time to time, too, given actor contracts and other real-world happenings.

But if the White Walker scene at the end of "Oathkeeper" is something Martin plans to reveal in a later book? That's controversial. It means that the show can and will reveal crucial story points well before Martin gets the chance, given that his final two novels, "The Winds of Winter" and "A Dream of Spring," have yet to see the light of day.

"A certain amount of that was inevitable," said Martin. "In an ideal world, the books would be finished by now, and I would've wrapped up the last two books, and I'd be in Ireland working with David and Dan on the show and writing one or two scripts per season. … But that's not the world we live in."

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Martin points out that in the end, "Game of Thrones" and "A Song of Ice and Fire" exist as "two different versions of the same story."

"That's pretty well true of anything you adapt. People make changes to Shakespearean plays or classics like 'Moby Dick.' Movie versions of 'Moby Dick' are not the novel," he said. "Once you sign a contract to do a television adaptation or film adaption, you have to be realistic. It's not going to be the same. It's another version of the same story."

Martin also acknowledges that building his story in the books requires fewer moving parts than what Benioff, Weiss and company require to bring "Game of Thrones" to life.

"It's two different mediums," he said. "Each one has its own demands. David and Dan are operating under some restrictions that I don't have: budget, shooting time… I can have a lot more characters than they can. I don't have to worry about putting actors under contract and all that. There are practical considerations going on there."

For some "Game of Thrones" fans, Martin's stance is perfectly reasonable. For others, not so much. Some book purists are sure to react to the promise of further changes as if they just got their heads squeezed by the Mountain.





Like it or not, those changes are coming. Better wear a helmet.

What do you make of the changes between "Game of Thrones" and the "A Song of Ice and Fire" novels?