It would be quite a simple task to summarize this, but that would make a joke of the complexity of the book, especially given the popularity of the tv show. Instead I will state my opinion trying not give too much away.
As whole the book is definitely complex and has most (if not all) of the trademarks of an epic fantasy novel. Some of the characters are very simple like Hodor, while in contrast some of them are complex in their motives like Jon snow, bastard son of Lord Eddard Stark. While the book starts out a little slow (in my opinion,) it steadily building lads up pace as King Robert visits Winterfall. After reluctantly accepting the title of Hand of the king, Eddward uncovers a conspiracy about the last hand of the previous king. Eventually things get out of control as the King dies, and Eddard challenges his son Joffery since he his the bastard son of the queen and her brother. After the Eddard is executed after being branded a traitor, his son Robb goes to war with the Lannister family.
The characters overall are characters you will love, you will loathe and those you tolerate. My favorite character would have to either John Snow, Tyrion Lannister or Daenerys Targaryens due to the complexity of their character and less then pleasant back story. I could bore with background for these characters but, I won’t. The characters I loathed entirely was Cersei Lannister and her son who is more like her puppet then her son.