I try to walk six miles a day, and I'm never without my Sony Walkman. I'm re-listening to "Charm School," by Nelson DeMille. Just about anything by Nelson DeMille is very exciting. I also loved "Red Rabbit," by Tom Clancy.
I've not been successful yet in listening to books. My comprehension doesn't work the same as when I read.
I've only tried to do that while driving though. I should try that while walking.