Well, for me (and I imagine, most) reading fiction isn't about trying to read as many words per minute as you can - it's about immersing yourself in a fantasy and enjoying the story.

Sometimes when I'm working offsite I have a long commute by hired car or train. Reading on a moving, bumping vehicle makes me feel really nauseous after about 20 minutes, so it's a no-no for me.

So, I find audio books great for commutes/land-based travel.

Back when I used to exercise, I enjoyed listening to audio books too.

Also, a good narrator can really bring books to life - it's a totally different experience than reading.