There is also Git user mailing list on Google Groups which is a nice place for beginners to ask about anything. + If you're a downstream packager of Git, consider joining the Git packagers mailing list for low-volume announcements from the developers, as well as other discussion related to packaging & porting Git.
If the manpages and this book aren’t enough and you need in-person help, you can try the #git channel on the Freenode IRC server (irc.freenode.net). These channels are regularly filled with hundreds of people who are all very knowledgeable about Git and are often willing to help. + The #git-devel channel welcomes Git development discussion, and might be able to help you contribute to Git.