Ixamyakxim: This is the sort of stuff that makes me a bit nervous as it seems like prime Season 6 plot fodder, especially as the show has left out the Greyjoys. Seems like (based on where last season left off) unless they're going to abandon a "North" plot beyond Sansa and Jon Snow (there's no way he isn't coming back ;) ) there's got to be some stuff in the books I haven't read that will be major events of the next (TV) season.
By the way, when is the next book supposed to come out? Before next summer? Or is HBO strictly now working off the "What If" sketch created in the event the show moved beyond the books / the book series wasn't concluded in time.
The understanding is that the TV series has been given the direction the major characters are going to the end. I would suspect that since the next book is in progress, they probably will have advanced copies of it.
I would almost say that its very likely at least some small points overlooked from the past books seeps into the next season. At the same time, a couple things might have also been clarified better in the TV series than the books so far. For example, I recall some people claiming that what the walkers were doing with the children was still very unclear in the books.
With the North, the whole "war south of the wall" has been changed around and simplified. The books dwell a lot more into various personalities and groups. Its far deeper than Stannis getting supplies from the Wall and marching on WInterfell. There is a lot more about attempts to gather support from others in the North against the Boltons. I suspect (having not read the books yet), this consumes a large portion of the story that has been written but not appearing on screen. The whole situation with Dorne is also completely different.
But generally speaking, from all the reckless speculation on the Internet, those who have read the books seem just as clueless as us TV watchers about what is coming next. I can only think of one really big "event" that book readers have been crying about being absent since the end of season 4 that would be a shocker if you've somehow avoided those spoilers thus far. By all appearances, it has been completely written out, but again, one never knows.
Other things have had their order moved, usually in the same season (for example, the Hound's injury didn't occur at the end of the season and Stannis didn't get a loan from the bank until after he had defeated the Wyldlings. So one never knows if they've just pushed something until later in the story...