The online book subscriptions arose simultaneously with the arrival of e-books. For a fixed monthly sum you can read magazines and books and listen to audio books. Services that offer these types of subscriptions are Bookchoice, Storytel, Leeslounge and many others. Some of them offer welcome promotions when you join, like a free book. Recently, for example, there was a T-mobile promotion where you got Bookchoice for a month for free with your subscription. As the free Bookchoice app allows you to read and listen to books on your phone.