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.[1]
Just an FYI, there is a new version of the book coming out in a few months which details the changes in Phoenix 1.3 [1]. Also, there is another book which explains how to build an app with Elixir only and then Elixir+Phoenix [2]. However, I haven't actually read it yet as I'm waiting for it to be officially released.
This was a good lesson for me not to get tech books well before I get a chance to read it. I got the 1.0 book thinking I'd read it when I get a break. Still haven't had a chance to do it and it is already somewhat obsolete. Live and learn :(
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.[1]
[1] https://www.amazon.com/Programming-Phoenix-Productive-Reliab...