I thought I would do a quick-and-dirty analysis of the popularity of the books vs. the seasons of the show.
A Storm of Swords was the basis for seasons 3-4 of Game of Thrones.
The book has a 4.54 rating on Goodreads, and those seasons each have a 97% audience rating on Rotten Tomatoes.
A Game of Thrones was the basis for season 1 of Game of Thrones.
The book has a 4.44 rating on Goodreads, and that season a 96% audience rating on Rotten Tomatoes.
A Clash of Kings was the basis for season 2 of Game of Thrones.
The book has a 4.41 rating on Goodreads, and that season a 96% audience rating on Rotten Tomatoes.
A Dance with Dragons was the basis of season 5 of Game of Thrones.
The book has a 4.32 rating on Goodreads, and that season has a 90% audience rating on Rotten Tomatoes.
So far so good.
Season 6 of Game of Thrones comes in at 93% on Rotten Tomatoes, which is a bit surprising to me, as I thought the season was really flailing. Some of the story material was mined from the not-well-regarded A Feast for Crows, which comes in at 4.14 on Goodreads. However, at a much-touted meeting with the showrunners, George R.R. Martin apparently poured out the answers to various mysteries and the direction of various storylines — for example, things to do with Bran, the origin of the White Walkers, Hodor, Aerys and wildfire, Jon, and Stannis—and these beans were all unceremoniously spilled in Season 6. I will say the finale of this season was magnificent, and probably colored the generally favorable reception of this season.
Seasons 7 and 8 of Game of Thrones are not based on any books at all, and they fall to 82% and 30%, respectively.
There are two remaining books which are being used as the basis for spinoffs. Fire & Blood is the basis of the upcoming House of the Dragon, but the book is a real snoozer with a 3.92 rating at Goodreads. A Knight of the Seven Kingdoms is better-liked but still no phenomenon, with a 4.21 rating at Goodreads. It will be the basis of the Tales of Dunk and Egg series.