I've never read the books, so I can't really judge how they're written. But when my mom wanted the series, my husband bought her the audio books and loaded them onto an MP3 player for her. The MP3 player spents months gathering dust until I suggested she listen to them when she's doing the dishes or folding laundry. (That's my trick to listening to audio books.)
A few weeks later, I called her when I hadn't heard from her in a couple of days. She was all excited about the progress she made on the audio books... Mom had started doing dishes, remembered the MP3 player, and started listening to the first Fifty Shades of Grey book. Apparently, she was totally into the audio books, because after the dishes, she also cleaned out the dog cage, pulled all the bedding, laundered the bedding and put it back on, dusted the entire house and scrubbed down the bathroom - all while listening to the MP3 player. LOL (I need to find audio books that engage me like that!) So she's a fan. And has a spotless house. Mom now wants a bunch of other audio books... but I'm afraid my husband would load "The Story of O", or any of the Sleeping Beauty series on her MP3 player because he's a twisted fuck like me. Contrary to popular belief, I usually *try* to shield my mother from the darker side of things.
Speaking of the audio books... one of my gaming buddies sent me a link the video of Gilbert Gottfried doing the Fifty Shades of Grey audio book... HILARIOUS.
http://youtu.be/5K1RcKJVbHA I DEFY you to not crack up.