The book has everything you need to know. The CDs are a teaching set. It really is a bad idea just to listen to them You need to follow the instructions otherwise you'll miss the how too of the process. Once you've done the course you can re-listen while driving or doing something else to pick up the extra ideas. They are explained differently than in the book.
Either way if you want to learn PhotoReading you must DO. You cannot learn it by just reading or listening.
Alex