But the early episodes of “Thrones” were burdened with the books’ stature and vast story. The changes that were made, like Daenerys’s wedding-night rape (a warning sign that the series would use sexual violence clumsily and too much) seemed to exist mainly for shock.

“Thrones” found its voice in “The Wolf and the Lion,” the fifth episode of that first season. The soon-to-be-late king, Robert Baratheon, sits with his wife, Cersei Lannister, to share red wine — their only common interest — and assess the sorry state of their realm. Westeros is troubled by schemers and threatened by invasion, and the only thing holding it together is their hateful marriage of convenience. “Don’t you get tired?” he asks her, ruefully. “Every day,” she says.

It’s a masterly exchange. In a few minutes, it lays bare their bitter relationship. It gives depth to the queen, who might otherwise come across a simple fairy-tale villain. It establishes the series’ perspective on the personal toll of political gamesmanship. And it appears nowhere in the novels.

For all its stunning set pieces — the battles of the Blackwater and Hardhome, the duel between Oberyn Martell and Gregor (the Mountain) Clegane — “Thrones” at heart is a series of conversations. Varys and Littlefinger. Jaime and Brienne. Tywin and Arya. Cersei and Lady Olenna. Tyrion and … well, anyone. In the Season 5 finale, the swordsman Daario, assessing Tyrion’s suitability for a search party, sums up his abilities: “So mainly you talk.” It’s true — and it’s why Tyrion, a disinherited dwarf, is the series’ most dangerous character.

Mr. Martin’s anvil-size books are more expansive. They include vast downloads of Westeros history and religion, outlines of genealogy and toothsome descriptions of banquets, which are vivid on the page — and should stay there. “Thrones” has lost some of the books’ majesty, but it has given them a much-needed edit, a Valyrian sword hacking through the expository clutter.