What is the difference between my book and the course? 

The course contains everything I have learned since coaching AND it is geared towards: QAs, devs and test automation roles. The book is just the tip of the iceberg! The course is a much deeper dive and 50% of the content you will never even have heard of like: The 4 questions every interviewer wants to ask you but can't, The #1 secret to nailing interviews, why you should almost never apply for tech jobs online + more.

So basically- the course is more in depth and feels like one on one coaching with me with downloads, videos and actionable steps (for an affordable price!).

At what stage of development should a beginner be looking into this then? 

Only 1% of people who start trying to learn to code ever actually get a paying job coding. If your goal is to land a job then everything you do in your learning to code journey should revolve around that end point. Day 1 you should be thinking about it.