iBooks autoplay audiobooks

I've discovered the joys of using iBooks to listen to my audiobooks. I listen to my audiobooks in the morning in the car on my way to work.

I've noticed that iBooks will auto-magically start playing my audiobook when I enter the car, even if my iPhone is still in my pocket (not connected to my audio cable).

So, although this seems like a really cool feature (iBooks AutoPlay) it is now becoming quite annoying since sometimes I don't want to listen to my audiobooks when I leave home from work.

How do I turn off this *almost* nice feature from autoplaying my iBooks audiobooks? I've looked in Settings and have not found the magic button to turn this feature off.