Why do I listen to a book instead of holding it in my hands and reading?
Sometime your hands need to be involved driving or washing dishes or cleaning the house or knitting. What you are doing may seem a bit of a drudge. Someone telling you a story keeps you company and makes the job seem to go faster. When driving, you may find slow traffic and stop lights good things as you get to hear more of the story. It can help you start you drive to work happier (you get to pick up where you left off after parking your car for the night.
Do I have any criteria?
Of course. I pick out books I might have bought. I listen to any sample I can find. A bad narrator can destroy a good book. If the voice of the narrator is irritating in a 30 second snippet, how is it going to be for hours of listening?!? I did try one because I knew the story was so good. I deleted it after suffering through 30 minutes!
Abridged vs. Unabridged
Unabridged! every time! If I would buy a book, I would read the whole thing so that is want I want in a recorded version. Abridged books, for me, are like cliff notes that give you skeleton version.
Tape or CD
I have some of both but my preference is CD. CDs won't melt in the car with the windows close to the 100+ temperatures we get in Texas. Also I've never had them get stuck in drive.
Last thought, if DH wants to sleep and I am not ready, I can continue the story in the dark with ear plugs and he can still have his dark quite room.