True, there's a fair few sites that will teach you for free. Code Academy jumps to mind. However, for those who like to read stuff instead, it's a decent purchase. (And the money goes to charity so...)
Well, yeah, but this is all digital content anyway. Read it on your PDF or read it on a webpage. There isn't a big difference. And I buy from Humble Bundle pretty frequently, so that charity guilt trip isn't going to work on me.
I'm not saying anything about you personally, nor was I trying to guilt trip. I'm just saying, some people prefer that kind of thing and there are other reasons people might decide to purchase it. I was just letting people know it existed...