I don't have HBO but is "Game of Thrones" worth following?
No spoilers, but some warnings:
There are currently 5 books published of a supposed 7 book series. It's up to you whether you prefer to read the books first. If you get into it, you're still in for a long wait. I would recommend avoiding spoilers if you're at all interested. (I usually prefer to wait until the whole series is complete before starting, but I was hearing too many spoilers so I went ahead and caught myself up on both books and the show)
The language/sex/nudity/violence is pretty graphic (some of the actresses are actual and former porn stars). So if that bothers you, put it on your avoid list.
The story is one of the most complex and multilayered I've ever read. It jumps into the middle of the events and the history/back story is revealed in pieces, leaving you to puzzle who is who, and how the events are related. It is not a cut and dry beginning-middle-end narrative. Reading the books definitely helps keep track of who is who and what's going on.
It does have magic, dragons, and other fantasy elements. If you like Lord of the Rings, you might like it. But Tolkein is childs play compared to this.
Although it is at its core a fantasy, GRRM put a lot of research into actual history in planning the events. Starks and Lannisters were modeled from the Yorks and Lancasters from the War of the Roses. There is also very little 'good guys' and 'bad guys'. Most characters are more complex and have both vice and virtue. But there are a few very bad guys.