It is a Digital / Virtual Master Tech holding your hand. Your training notes and some, searchable, easy to get at.
Economically, if it helps you nail just 1 or 2 tricky jobs then it's paid for itself.
Not a substitute for structured classroom / workshop training but an excellent complement to. Plus it would be impossible to accurately remember all the facts and figures taught to us.
You can add your own notes to Fault codes, symptoms etc. so a good way of keeping a diagnostic diary / library for future reference. If it is missing something, you can add it yourself.
As with anything from James, it will be as good as he can make it.