I recently started using the audible books and it works well with the Sync in the dog truck. In a cool little trick that I don't use you can listen to the audio book and then have the ebook in the kindle app and when you open it up you are where you left off in the audio book.
My regular truck doesn't have the capability to plug in the iPhone, etc and the CD player just died and I had to get through about a 30 hour trip with no audio books. So I have been looking into other options. You can add the ability to plug the iphone into your current stereo. Parts are about $175 bucks at Best Buy or Crutchfield plus installation, unless you can do it yourself. I may just get a new stereo, though--although the 2014 F150 Platinum is a nice idea as well.