According to the New York Times, erotica and even somewhat naughty novels are a smash success in the audio book market. Typical consumers range from salespeople to long-haul truckers. Even the car-pool parent or subway commuter occasionally succumbs. That may explain sudden stops made by tractor-trailers or the secret smiles on the lips of your Metro seat-mate.
Poor DH Lawrence and his pals wouldn’t even raise an eyebrow today.