I've read it and three things I can say were really good about it were the incredible diversity and number of characters and events, detailed and realistic worldbuilding, and straightforward, direct storytelling. Those things make it a fantastic story to read for people who want a realistic, plot heavy story that doesn't dance around inconvenient topics.
Those of course can be heavy turn-offs for some people, becuase many people won't like the very slow pace and sometimes even offending topics, but there are few books that do that properly, making GoT really unique.