John Scalzi's latest book - The Dispatcher - was written to be an audiobook.
Which is interesting because writers generally write to draw pictures in the reader's head. In this case, the writer was one step removed from the reader, and had to think about how his narrator - in this case, Zachary Quinto - was going to read it.
Special care was taken to ensure each character had a very individual way of speaking, as well as largely eliminating the "he said/she said" that we are so used to in books.
As a writer, this is a very interesting article to me... it's that halfway point between a screenplay and a book...
And definitely gets my brain juices flowing!