That book is great, and so is the built-in gittutorial(7). If you really want to get down and dirty with Git, I'd also strongly recommend going one step further

That book is great, and so is the built-in gittutorial(7). If you really want to get down and dirty with Git, I'd also strongly recommend going one step further and reading gitcore-tutorial(7). It shows you the man behind the memorized commands curtain.