How do the actual story ends in the books?
It doesn't, and therein lies the problem.
The series was supposed to be seven volumes but Martin only wrote 5. The sixth was supposed to bring on winter and the Night King, but never got written, although there were rumors it was underway. Nothing about the seventh.
That’s just it - Martin hasn’t finished the books, so there is currently no end to the story..aside from what the show writers come up with.
Martin has apparently given them an outline of how things end..but has also said that aside from the overall gist that story arcs for “secondary characters” (which could include pretty much anyone aside from Daenerys, Jon and Cersei) are likely to be much different when..err..IF..he finishes the books.
Not in book form yet - too much money from HBO
They don't. George R.R. Martin never finished the last two books. I am pretty sure that the 2 producers, when this show started, figured that he would at least finish one of the books while they were filming the earlier ones, so that they would have his source material. But, it has been a long, long time since his last book was written and there is no date as to when the next book was coming out. So, the proucers had to improvise; and, unfortunately, they are not the writer/storyteller that Martin is. So, a very disappointing season 8.