Okay, I know that I'm one of thousands of voices stating how amazing this book is, but the thing is that I frequently say books are so-so or awful, and I say that this one is amazing. It's so good.
It's the characters. You have to love a book with good characters. More than that, the story is complex enough to keep you guessing, but not so complex that you lose interest.
The biggest thing for me is the character development that Daenerys undergoes. She is a frightened, weak, child at the beginning. And if you want to know how much she grows, you'll have to read it.