Right now, Game of Thrones is in it's 3rd season (it was picked up for it's 3rd season just 9 days after premiering it's 2nd season) and is an adaptation of the 3rd book in the series. The cast and characters are all incredibly dangerous and fascinating which makes the show so intriguing. I can honestly say (with out reading the books of course) that at this point in the show ANYONE could die. This is highly unlikely for a TV show to kill off it's main characters but the show has done it before and would not be a surprise. The premise of the show obviously revolves around a fictional fantasy world where kings and queens ruled the land, so naturally the goal of the majority of characters is to become the king. And I can say it's a very safe bet that any one of the characters has a rightful power for the throne.
Some of the favorites on the show include Peter Dinklage as Tyrion the women-crazed son and imp of a very wealthy family who strives for the kingdom; Emilia Clarke as Daenerys Targaryan the bad-ass blonde dragon trainer; and Kit Harrington as Jon Snow the young and hunky bastard-son who's gone on to fight in a brotherhood army. (Emilia Clarke is my favorite - I actually met her when she was starring on Broadway!)
The show brings on a huge cast of characters yet does a wonderful job of including them and weaving in story lines. (Unlike Glee with all of their characters). I will continue to watch this show for as long as it will go on for a while. There are 5 books currently but 2 more in the works and they might split the books up into multiple seasons as they did for seasons 3 and 4 (both about the 3rd book).
Could HBO be onto something, but turning hit books into TV shows rather than movies? (True Blood is another example.) Maybe Harry Potter should have been an HBO series? But then again it probably wouldn't have had enough sex or nudity for HBO to pick it up in the first place!
