BuddyPress.org

Now this is just my honest opinion, but I wouldn’t get it (this isn’t a slight against Lisa).

If you glance the TOC, it’s more of an introduction to BP, which is great if you don’t know anything about WordPress or BuddyPress and you’re just diving in. And, you’re right, you can find most of this info online.

If you are an intermediate developer (or if you’re experienced with WP), you can learn as you go and dig through the BP code and other BP plugin’s code.

FYI, WPMU.org is not an affiliate site.