One thing I do know about audiobooks: the narrator is extremely important. Many non-audiophiles are leery of audiobooks because they feel like it's just too weird to have someone read a story to them. And that's where a narrator comes in. The best narrators perform a book, rather than just read it. In fact, I often search Audible.com by narrator to find new authors to try.
My favorite narrators:
Barbara Rosenblat: She does all of Elizabeth Peters's books, but my favorites are the Amelia Peabody series. She also does Katie MacAlister's dragon series and the Recorded Books version of Kathy Reich's Tempe Brennan series.
Jim Dale: Famous for his Harry Potter narrations, he also does the Peter and the Starcatchers series.
Jim Frangione: It took a bit of time for the voice of JRWard's Black Dagger Brotherhood books to grow on me. Now I can't imagine anyone else reading them.