I love this book. It's what helped me move from an intermediate Git user to an advanced one, and I've subsequently trained a bunch of people at different organizations by going through it.

However, Pro Git is not an ideal resource for newbies unless they are highly motivated or receiving generous training. A simple graphical representation of your own repo goes a long way towards establishing a mental model of what Git is doing internally — which is in my view the chief insight of mjburgess's post at the top of this thread.