What I found to be of particular interest was this paragraph:
Two Penthouse magazine books, “Between the Sheets: A Collection of Erotic Bedtime Stories” and “26 Nights: A Sexual Adventure,” were released in download-only audio versions in 2002, but like the books’ temptresses, they have had long legs. Sales remained so brisk that in 2006 “Between the Sheets” was the bestselling download-only title on Audible. So in August, four years after they were first recorded, Random House Audio released both titles on CD. With 7 of the top 10 download-only sellers on Audible in the erotica genre, the company has been a trailblazer in the category, albeit a conflicted one.
So, once again, porn and erotica are leading the way in an emerging market on the Internet. Though it also shows that the sound of words remains fundamental to the composition of a book. To me, there are some books that always read aloud better than inside my head. Judging by sales on Audible.com, erotica always sounds good aloud.