Audible US is having a 3 for 2 credit sale on trilogies and there is plenty of great content available. Normally audiobooks cost one credit and each credit costs $15. Three books for two credits makes the cost of each audiobook $10, which is a great deal. I would recommend the Passage trilogy by Justin Cronin and read by Scott Brick.
Michael Kozlowski is the Editor in Chief of Good e-Reader. He has been writing about audiobooks and e-readers for the past ten years. His articles have been picked up by major and local news sources and websites such as the CBC, CNET, Engadget, Huffington Post and the New York Times.