User blog comment:Gcheung28/Game of Thrones Returns in April/@comment-5014364-20140113014647

Remember:  the third novel is the longest so they split it into two seasons:  thus "Season 4" is the second half of "Book 3"....containing the *actual ending* of Book 3.

One of the reasons the Red Wedding was so shocking in the novels is because it happens long before the expected climax, like two thirds of the way in. It was sort of like how Renly died in episode 5 of Season 2:  NOT near the climactic end and thus very shocking. I sympathize that the TV series needed *something* to make the Season 3 finale center around and the Red Wedding was sort of obvious, but it lacks a bit of the punch from the novels (it would have been so much better in episode 5 or 7).

​At any rate, the result is that Season 4 contains the *actual* "climactic ending" of Book 3. Well, endings plural, what with multiple storyarcs and all.

Moreover, the book series was originally conceived of as a simple trilogy, but then grew in scale as GRRM wrote it:  the ending of "Book 3" (now adapted as Season 4) was going to be the ending of the ORIGINAL first novel.