I have the course, but I have seem many book-only people post of there success. I would say that the choice should me more dependent on you availability (money), your learning style, and your likeliness of staying with and using the system.
If you feel confident you will plow through the book and do what it says and commit to it. Then the book is perfect. If you think that the audio course will help you get through the system and use it then go for it.
You can learn and use the system.
You are perfection.
Iam2 
