I loaded the book on to my phone last night and read the excellent foreword by @FrancescoC, where he says when he asked José what problem he was trying to solve José said that he wanted to bring the power of Erlang to other communities. Francesco goes on to say he had put the same question to many other language creators but José was the first to say his focus was on the adoption of ideas, semantics, and run-time (of the extremely powerful Erlang) and he did it by approaching the problem with a different syntax, tools, and development approach.
In more simpler terms (and something many of us have been saying on places like the forum) his goal was to essentially make the power of Erlang as accessible as possible to people who have learnt or have become accustomed to what some might consider ‘modern’ languages and frameworks, such as Ruby and Rails.
I’m glad Francesco got it directly out of the horses mouth and when people ask this question in future I will point them to this post! 
PS, if anyone is interested here is my review of the original edition of this book: Elixir In Action (Manning) - #2 by AstonJ
