If you want to learn Git from the inside out, I wrote a two-parter that aims to explain Git from the inside out, focusing on the data-structure Git uses:
Finally, _if_ you have an O'Reilly subscription, I am currently writing Head First Git (first four chapters are in early release). If you are not familiar with the Head First series, its a rather unique format that involves using lot of pictures to explain ideas and traditionally the books move a lot slower than most technical books. Ideas/concepts are cemented using puzzles, quizzes, crosswords.
