Audible is my long-time favourite source of audio books. My only focus when acquiring audio books are to look for business educational and inspirational topics. I use it as part of the 5am club of Robin Sharma in training my mind daily and using it while commuting in my car to clients or other travels.
The great thing about Audible is that they give you two FREE books with your initial sign up.
Thereafter you have the choice to opt into the monthly membership to purchase an education book monthly. You can also decide to purchase as you choose. I prefer the monthly subscription because it forces me to keep learning J
Get you 2 FREE audio book in this linkAudible Free Trial [Digital Membership]