Because I have read the 4 four books, (every season completes 1 book), I knew more or less what to expect, and so far I have to say that im perfectly satisfied!
The production is from HBO, whıch has made some very good series in the past. (Band of Brothers for example), so I had no doubts for the quality of these series. But because the main thing on these books is the detailed written and the very 'strong' characters, I was waiting to see what they did on this matter. Well, I have to admit that they have done some great job!
The whole story is about Westeros, a big Continent (?) with 7 kingdoms each one ruled by it's own lord, and alltogether ruled by a king. In the north a great wall made of ice protects the kingdoms from the wild tribes that live 'out there', and in the south the narrow sea separates them from another part of land in which 'savages' live, and it reminds sooo much of Africa...
The seasons are not in the way we know them. They had a summer period for the last 4 years, and now they are in the brick of the long and dark winter.
It's impossible to write what's going on in these books (or series if you like), without revealing things, so I'll stop here. (Btw, the rating for the 1st season on imdb is 9.4!)
I recommed to every one who likes fantasy even a little bit, to watch the Game of Thrones, cause they made a great job based on some very good books!
Be prepared! The winter is coming...