George RR Martin says the writing process has taken the ending of the A Song Of Ice & Fire book series “further and further away” from the Game Of Thrones TV series. He suggests there’ll be more differences than similarities.

Writing on his blog, Martin repeated an analogy he has made several times: he thinks of his writing process more as being a gardener than an architect. In other words, while he makes plans, there’s plenty of scope for things to change along the way.

Martin says he’s very reluctant to give any details about the development of the final book, The Winds Of Winter, noting that even his recent reference to a chapter about Tyrion Lannister reveals that (at that point at least) Tyrion remains alive, a form of spoiler.
He adds that:

What I have noticed more and more of late, however, is my gardening is taking me further and further away from the television series.   Yes, some of the things you saw on HBO in GAME OF THRONES you will also see in THE WINDS OF WINTER (though maybe not in quite the same ways)… but much of the rest will be quite different.

According to Martin, this isn’t primarily a matter of different visions, and he’s perfectly happy for people to make comparisons between the books and TV show when he’s completed the saga. Instead he explains that the combination of the books having more detail and him getting further down the writing process means that even minor variations open up more paths, and even more characters, meaning the differences become greater.