I love audio books.
One of the reasons is that I live alone and I like someone to read a story to me before (or while) I fall asleep. For these, I choose books I've already read/heard before (and I DO reread and re-listen to books in my library).
Like many people, I enjoy listening to books while driving, particularly on long trips.
And I also use new books and/or new audio books as a reward for doing good work, or making wordcount.
Last night I gave myself a guilty pleasure and listened to an audio book, Sweep In Peace, by Ilona Andrews.
Advice first, then ramblings. Audio books are GREAT for getting the feel of the language, of different accents and rhythms of speech from Jane Austin's upper class British to an east Texan twang.
When I first started listening to audio books, I listened to old favorites of Jayne Ann Krentz. To my surprise, the reader put the emPHAsis on different words and phrases than I did. It was both disconcerting and illuminating. There's old common wisdom that you should read your work aloud (I don't have time with the schedule my publisher wants), and we do this at my critique group. It can help immensely, particularly if you have a run-on sentence or one of the made up words (like chwisge – whiskey) to see what works and doesn't. Sometimes I won't change a very alliterative sentence or an awkward one, but most of the time I do.
The best audio books I've ever listened to are the Elizabeth Peters historical mysteries read by Barbara Rosenblat. They are just incredible, particularly the ones that have the boy Ramses growing up, Ms. Rosenblat ages his voice...(and one of the best titles ever is The Last Camel Died At Noon). The Harry Potter audio books are exceptional, too.
I won't say the worst I've listened to – mostly because of the books themselves, not the authors' best works – but sometimes the actor screws it up. I listened to one where the actor made the hero's voce sort-of upper crust nasal, this was a ROMANCE and the hero didn't sound acceptable.
My absolute favorite audio books are romances where a husband-wife team read the hero/heroine's point of view, such as Smoke and Mirrors by Jayne Ann Krentz, and Linda Howard's Kiss Me While I Sleep. When Dick Hill makes the car noises, it had me rolling...
And since I love audio books, I am more aware of dialogue in my books, providing enough tags or movement so that my narrators have the cues they need to change their voices for different characters.