Collecting the best books mentioned on hacker news, reddit and other places
Before getting my feet wet, I also purchased a lot of books. But, in the end, the best way I realized was to start building something like a TODO app. I started with an ECommerce website (whoa) and was pleasantly surprised. Of course, my strong background in Rails helped me quite a lot, too.
If you want a really good book that helps you understand concepts (and also the code) the best one so far I've read is Programming Phoenix by Chris and José themselves.