Whether in written or audio format you cannot go wrong with A Song of Ice and Fire, each book brings more than the last and is masterfully written! the narrator is wonderful and easy to listen to as well!
The book is amazing (of course), but some of the voices the narrator used are almost unbearable. Varys especially, he sounded like how a deaf guy sounds when he talks. Tyrion sounded like a leprechaun. BUT, the narration becomes a lot more enjoyable if you change the speed to 1.25x