I would recommend reading these 2 books in parallel: Elixir in Action by Sasa Juric (one of my favorite programming books in general), and Programming Phoenix from PragProg. And before that, to wet your appetite and get a feel for the Erlang VM, watch a small video by Sasa Juric on youtube: https://www.youtube.com/watch?v=JvBT4XBdoUE