What separates Martin’s books from the pack is that his made-up world of Westeros feels more “real” than other made-up worlds like Tolkien’s Middle Earth or Brooks’s Shannara. There’s very little magic in the series, and when something supernatural happens, everyone is freaked out and confused. The characters have sex (mostly sex that would be illegal today), get tortured, betray one another, and die incredibly easily and often for very little reason—just like real people involved in a medieval war would have. One of the first plot points is a child getting thrown off a ledge and crippled after he witnesses some nasty-ass incest; one major character gets killed on the toilet and shits all over the place as he dies. So the books are earthy, you might say. More importantly, anyone in Martin’s world who strives for nobility, honor, or any other trait lauded in traditional fantasy novels inevitably ends up impaled on a spike or crippled and humiliated by the amoral crooks who always come out on top. Like I said, this is more realistic than most epic fantasy.
Naturally, a show based on a series of books that’s full of plot twists, reversals of fortune, bloody battles, and scheming villains is gonna be a slam dunk. Throw in HBO’s typically high production values and strong performances (and lots of nudity) and you’ve got a recipe for a pretty fucking sweet franchise, son. You mentioned that you don’t appreciate the “scope, escapism, narrative skill, and subtle humor that fantasy fans eulogize,” but there’s nothing subtle about Game of Thrones’s appeal. It’s all, “OH SHIT HE’S GETTING KILLED WTF” and “AWWWW DAMN THEY’RE CUTTING HIS DICK OFF!!” If you refuse to watch that because—what? It’s set in a vaguely medieval world? There are dragons in some of it?—I don’t know what to say to you.