I feel like I need to write a review for this, so here goes nothing...
This is a very, very well written book, and I love how much thought went into the world itself. The characters are absolutely amazing; I honestly don't know how George R.R. Martin decided on different names for the characters, their houses, and even individual landmarks such as rivers and towns.
The only problem for me was the amount of sex throughout the book; I'm usually fine with a bit of this throughout (the author is trying to create a relatively realistic world after all) but I personally felt slightly uncomfortable with the frequency and amount of detail it went into, and found myself wondering when I would be able to continue with the actual storyline instead of reading about the 'needs of men'.
Other than that, I thought it was a good book and would recommend for the more mature reader.