Read them all at once. The difference is striking. And yes, 4 and 5 are "utter shit" compared to the first three.
i like how something that's arguably not as good as the previous iterations (which 99% of the time will be subjective to every individual member of the audience) is instantly "utter shit".
potential book spoilers
Martin is unquestionably a good writer, but he stopped being an author in the past two books. Writers string words together. Authors tell stories with words. The difference is most striking if you go back and read some of GoT immediately after finishing DwD. In GoT, the story snaps along. There are few if any random fluff chapters. Time spent going from point A to point B is left to the reader's imagination unless a relevant plot detail needs to be revealed. Compare Ned going to King's Landing to Tyrion's travels in Dance and it's incredible how much Martin's discipline and sense of purpose have degraded. Or the Victarion chapters. Or the entire Dorne arc. Somehow between books 3 and 4 he got it in his head that people like his work because it's excessively detailed, not because he was constructing a good story with a clever plot and good pacing, so he answered with thousands of pages of fluff.
It's fun to take a look at the amazon reviews for the first three books and compare them to those for the last two. Zealous fans of the series might read 2000+ pages of loving description of Tyrion's plot-irrelevant day to day life and give it five stars, but the distribution of votes takes a wild turn for the worse with book 4, and gets worse still for book 5, for the simple reason that the vast majority of people want story, not writing. I hope he figures this out for the next book, but I have little reason to believe he will. His editors failed him with the past two books and I doubt they're going to turn it around for book 6.