Listening to audio books in the van is working exceptionally well for us. First Son has not shown a great deal of interest when I've read longer books aloud at home (though we still read through them together). In the van, however, he's a captive audience with little else to grab his attention. He seems to enjoy the stories and asks us to turn them back on if the stereo is off when we start. Many of the ones I'm selecting now I'm hoping he will read next year during his "reading lessons" (really just First Son reading while I really listen, not while I make dinner or wash dishes or something).
We recently finished listening to all seven of the Chronicles of Narnia. For most of the books, we just listened to someone reading the text. When I had expended all my renewals, we borrowed The Chronicles of Narnia: Innovative Audio Entertainment with Complete Cast, Cinema Quality Sound, and Original Music (19 CDs, 7 Complete Audio Dramas) (Focus on the Family Radio Theatre) from Grammy. At first I was disdainful of the "8 and over" suggestion on the back, but now I know better. In one of the first chapters we heard (we listened to the books out of order), Aslan chased Shasta, Bree, Aravis and Hwin together. First Daughter in particular was quite frightened. Even First Son was upset until I explained it was Aslan and that he was actually helping them in their journey. It was also more difficult to First Son to follow the story as some points. I still don't think he realizes that Aslan turned Rabadash into a donkey at the end of the novel.
In general, I'd recommend choosing a straightforward reading for the audio books when young children are in the vicinity. Of course, you can read the books out load yourself as well. That doesn't work so well when you're driving, though.