A confusion of sorcerous proportions

Will somebody please  explain to me what is going on with George RR Martin and A Game of Thrones?*

Time was when we fantasy nerds inhabited a small but well-furnished bubble positioned to the side of the main pool of readers – people who read ‘normal’ books.  These days, though, every man and his dog seem to be asking for and talking about this hit fantasy series.  And there’s not even any sparkly vampires involved …

I haven’t actually read Martin’s best-selling books, but a significant number of customers are sidling up to the desk here in the library and telling me in confidence, “… normally I NEVER read this kind of book, but they are really amazing!”

So tell me, fantasy newbies, what’s so great about A Game of Thrones?  And should I read the books? Watch the TV series? Both?

(* NOT a rhetorical question, folks.)