You can start where you like, although Perfect cookies 1 starts you off with a great base of recipes and explains in detail Bec's method for making perfect cookies in a processor.
The first course will prevent any common cookie mishaps, spreading, how to make crunchy or chewy cookies and a whole range of other cookie issues are solved. Perfect Cookies 2 Course assumes you have a basic understanding of baking cookies but is filled with extra tips to make your cookies more like what you'd buy from your local cafe.