The following is a list of differences between Season 7 of the TV show Game of Thrones and the A Song of Ice and Fire novels. While all the plotlines in the show are ahead of the point the novels reached, there are still many differences between the episodes and the material source.
Bowen Marsh, not Robett Glover, expresses his disapproval of Jon's idea to garrison the abandoned castles of the Watch with wildlings.
The Umbers have never betrayed the Starks: Greatjon was captured by the Freys, Smalljon was killed in the Red Wedding while defending Robb Stark, and Mors Umber joined Stannis. Only Hother Umber has joined the Boltons, but reluctantly because Greatjon is held prisoner by the Freys; he is by no means loyal to the Starks' enemies.
It is Godry "Giantslayer" Farring, not Yohn Royce, who suggests destroying the Last Hearth. Jon objects, explaining that the Umbers are not traitors, and that such act would turn the whole North against Stannis.
There is no character named Ned Umber in the novels.
There is no mentioning in the novels that Smalljon Umber had any children.
Stannis did not leave Dragonstone unoccupied. He left there a garrison before traveling to the North. In the fourth novel, Loras Tyrell conquers the castle on behalf of the Crown.
Cersei never had any intention to ally with the ironborn. She refers to them scornfully as "a sorry pack of squids".
The ironborn never broke any promises and never allied or befriended with the Starks, or with any other of the houses who participated the War of the Five Kings.
No one stole the Iron Fleet from Euron, and he did not order to build even one ship (let alone 1,000). He sent the Iron fleet, under the command of his brother Victarion, to the Slaver's Bay, and still had hundreds of ships at his disposal to raid the Reach.
There is no naval battle in the books between Asha Greyjoy and Euron. Asha is defeated and captured by Stannis at a much earlier point in the novels, before he marches to Winterfell; Euron, Ellaria and the Sand Snakes are not involved at all in that battle; the main part of the battle takes place on the mainland.
Euron lets others (mostly his brother Victarion) do the fighting, while he makes the plans and stays safely behind.
Euron prepares to fight the Redwyne fleet. He does not care about Asha.
Ellaria and all the Sand Snakes are alive and free.
There is no mentioning in the novels that Cersei insisted on breastfeeding Myrcella. Generally, she has always focused on Joffrey, and hardly paid any attention to Myrcella and Tommen.
Cersei says in the show "I never got to have a mother". In the books, Joanna Lannister died when Cersei was seven years old, thus had enough time to get to know her mother.
Jaime and Cersei had sex for the last time after he returned to King's Landing, next to Joffrey's corpse. Ever since then, they have grown distant, and loathe each other.
It is not Tycho Nestoris but Noho Dimittis, another representative of the Iron Bank, who meets Cersei in the novels. The meeting takes place much earlier, and Cersei refuses to pay off the debt of the Iron Throne. Therefore, the Iron Bank decides to loan Stannis the funds he needs.
The Iron Bank never invested in slavery.
Tycho Nestoris talks about dragons with Jon, not with Cersei.
Xaro and a custom officer named Qavo, not Tycho Nestoris, complain that Daenerys's disruption of the slave trade has had severe economic ripple effects across Essos. They do not tell that to Cersei.
Cersei was partly responsible for Ned's death, but had nothing to do with the murders of Robb and Catelyn.
Tyrion never made any tunnel inside Casterly Rock for sneaking whores. In order to meet Shae secretly, he used a secret tunnel leading from Chataya's brothel to a stable, and for the same purpose he used secret passages inside the Red Keep.
The lesson Jaime has learned from the Battle of the Whispering Wood is the opposite in the books: he does not use Robb's strategy against enemies - instead, he takes precautions to make certain he will not be taken by surprise again.
There is no mentioning in the books that Jaime suffers from reading disorder.
The gold mines of the Westerlands have not run dry in the books, they are as prosperous as ever.
Jaime was not present when Joffrey died at his wedding feast. He and Brienne arrived at King's Landing some time afterwards.
Jaime has no idea who is Joffrey's murderer, and does not really care, because Joffrey meant nothing to him.
Tyrion, not Olenna, calls Jaime "poor fool", taunts him for being Cersei's minion and claims (falsely) that he murdered Joffrey.
Tyrion has no idea that Jeor Mormont is dead, and by whom. As far as he knows, Mormont might have been killed by wildlings.
Bronn has already received the reward Cersei promised him - married Lollys Stokeworth and took possession of Castle Stokeworth. He does not make any on-screen appearance after his last conversation with Tyrion, in which he refuses to fight the Mountain.
There is no mentioning in the novels that the Golden Company was ever hired by the Iron Bank to collect debts, or for any other mission.
Cersei never considered hiring the Golden Company. Currently it is hired by a new contender, who has not appeared yet in the show.
The identity of the person who sent the catspaw assassin to murder Bran is revealed in the third novel - Joffrey.
Arya reacts indifferently when she hears about Joffrey's death.
Joffrey was never the first on Arya's hit list. Nearly every time she recited the list (before learning about his death), he was one before the last.
Arianne Martell and her companions Elia Sand and Daemon Sand are the ones who find ancient carvings on the walls of a cave.
Melisandre used Edric Storm's blood for the leech ritual, not Gendry's.
The Watch has never taken any punitive action against the mutineers. Jeor Mormont's death is partly avenged by Coldhands, who kills five of the mutineers (among them Ollo Lophand, the one who killed Mormont); it is unknown what has become of the rest of the mutineers. Jon and Jorah have no idea about that.
Arya has never shot even one single arrow in the novels.
Tormund is not red-haired. His hair and beard are white as snow.
There are 500,000 residents in King's Landing, not one million.
There is no mentioning in the novels that the ironborn kill defective babies at birth, as an act of mercy. It is done at the pirate dens of the Three Sisters.
Cersei tried to get Tyrion killed only once - by the court trial. In the books, it has not been confirmed that she sent Ser Mandon Moore to kill him.
Cersei believes incorrectly that Tyrion is guilty of Myrcella's near-fatal injury, but her suspicion has nothing to do with Tywin's murder. She thinks Tyrion hired Ser Gerold "Darkstar" Dayne, who attempted to murder Myrcella (she survived but was permanently disfigured).
Cersei still believes Tyrion is guilty of Joffrey's death, thinking he and the Tyrells conspired together to kill him.
Theon never thought Eddard Stark was a father to him more than Balon. He said once that Eddard was a second father to him, but it was only a lip service: to him, Eddard had always remained the man who'd brought blood and fire to the Pyke and taken him from his home.
Asha never attempted to rescue Theon. Currently they are held captive at Stannis's camp.
Theon's physical condition is so poor, as a result of Ramsay's torturing, that he cannot put up any fight against stronger opponents, whether he was castrated or not.
Sansa knows firsthand that Littlefinger made Lysa murder her husband, and also made her send Catelyn the letter in which she falsely accused the Lannisters; Lysa blurt that out in Sansa's presence, shortly after she tried to push Sansa through the Moon Door.
Littlefinger never denied the dagger originally belonged to him; similarly to the show, he said that outright to Catelyn and Ned in the first novel. His lie was about the identity of the person to whom he lost the knife in a bet, which was not Tyrion but Robert. Moreover, Littlefinger had nothing to do with the failed attempt on Bran's life - it was Joffrey who armed and sent the catspaw assassin.
The Golden Company consists of 10,000 soldiers, not 20,000.
The break up between Jaime and Cersei happens in much earlier point in the novels: it begins toward the end of third novel, right after they have sex for the last time; throughout the first half of the fourth novel, they grow to loathe each other very deeply; Jaime even contemplates killing Cersei. Finally, at the end of the fourth book, Cersei writes to Jaime to come to her aid, but he turns away from her because he no longer loves her, and found out she sleeps with other men and is guilty of all the crimes she is charged with (high treason, incest, adultery, fornication, regicide and decide).