Some books are adapted to the medium of audiobooks better than others. A mediocre narrator can taint what is otherwise a great story. Likewise, an outstanding narrator can uplift what is an average story.
For me, His Dark Materials is the best audiobook I've listened to. It's read by the author, and has a full cast of (fantastic) voice actors for each character, it brings the story to life so wonderfully. To the point that even if I read the book now, I hear a good amount of the voice cast speaking for each character.
If you haven't heard it, I can recommend it! Honourable mention goes to Stephen Fry reading the Harry Potter series.
What is your favourite audiobook?