WTF Is Game Of Thrones And Manhattan/Westeros Nerdism All About?

Add this to the list of stuff I don't understand: the all-consuming nerd mania over the HBO show Game of Thrones.  There seems to a ton of really involved fandom, and enthusiastically interpolating the fictional Westeros and the somewhat less fictional Manhattan is only the beginning.  I don't get it.  As far as I can tell, the show is pretty much typical, if somewhat more expensive, HBO/Skinamax type stuff; even skeevy places like Huffpost get that.  I mean, I like gratuitous nudity as much as the next person, and HBO has been serving up similar material without fail all along throughout its history, but this particular is show is also all the rage beyond the prurient.  So what makes GoT so different that seemingly (mostly) normal tee vee nerds consumers go so crazy?  Can it possibly be the source material?  How?  I have always found George R.R. Martin to be unconscionably tedious, like a super-low-budget Tolkien.  Fortunately for me, I probably don't have the time, but I am genuinely curious why charming fantasy geeks are so taken.  More than likely I will never know the answers to these questions, but tune in next time for another episode of Bullshit, or Not?

Update: A view from the other side.  Different, more seasoned, demographic, perhaps.

Updater: Dude has some good taste in Pogues songs, though.  She's written an excellent essay on "Fairytale of New York" that I think would warm the hearts of Shane MacGowan and Jem Finer, and it certainly should be read and appreciated by fans of that great song in particular and The Pogues in general.