YMMV / The World of Ice & Fire

• Broken Base: There are the those who are excited for some new information on the world and history of A Song of Ice and Fire, and then there are those who wish Martin stopped wasting time he should be spending on The Winds of Winter. Others appreciate the worldbuilding aspect but disparage the quality of writing, particularly as it's often painfully obvious which parts were written by his co-authors.
• Complete Monster: See here.
• Designated Hero: House Blackwood. Where the main series criticized Feuding Families with good and bad elements on either side and where a memorable moment in A Dance with Dragons has one of the Blackwoods accompanying Jaime as a hostage to the crown mention how Blackwood and Bracken have a long history castigating one or the other. The series lore is clearly favorable to the Blackwoods, since every named Blackwood mentioned in more than a few sentences and paragraphs is shown as an infallible, morally upright badass, while every Bracken is unpleasant, cowardly or traitorous, or some combination of the three. This extends to the Great Bastards. Bloodraven, the son of Melissa Blackwood, is fanatically loyal to the Targaryens, ushers in a time of peace in the Seven Kingdoms, and is good at everything he does, whether he is Master of Spies or Lord Commander of the Night's Watch. Bittersteel, the son of Barba Bracken, is a skilled knight, but a Jerkass who fails again and again and again, and dies in exile with nothing to leave behind except the Golden Company. Maester Yandel makes it really obvious which family is the more heroic one. One can argue that this is an invoked trope since as an in-universe academic record^note obviously the House that eventually married into the royal family and stayed loyal to the Crown (and whose Great Bastard served the realm with great distinction) will be portrayed far more favorably than the house that fell into disfavor with the Crown and whose Great Bastard helped to incite open rebellion, except as per the Meta Origin (written during the reign of Tommen Baratheon), the Brackens bent the knee to the Lannister Regime, while House Blackwood was still resisting until late in A Dance with Dragons.
• Hilarious in Hindsight: This book introduced a Tully ancestor named Lord Grover Tully. Along with his grandson Elmo and great-grandson Kermit, he's an obvious Shout-Out to The Muppets. Later Sesame Street did a Game of Thrones parody titled "Game of Chairs" with Grover as the main character. He ends up winning the Iron Throne. Then years later, after HBO got distribution rights to Sesame Street, Elmo came to Westeros and met Mr. Tyrion and Ms. Cersei as part of the "Respect Brings Us Together" promotional campaign. Elmo's suit of armor features his goldfish Dorothy as his emblem, but a leaping fish is also the symbol of House Tully...
• Memetic Mutation:
  • "And there are no children in Asshai."
  • Oily Black Stone shows up everywhere, which has spawned an entire Epileptic Forest.