Free section of 'Mastering Git' book:
http://cdn.oreillystatic.com/oreilly...754_Sample.pdf
BTW:
PacktPub gives away a free e-book a day.
Look for 'Free Learning' on their website.
I have several hundred from them.
You don't get to pick the topics like that, and the quality may vary, but free as in you click the button and they are yours.