If you really want to learn Elixir, you should learn enough Erlang prior, to get a better understanding of how Erlang/OTP all fits together. Thus, I would recommend the following structure:

1. Read Joe Armstrong's Book: Programming Erlang to learn the basics and the philosophy behind Erlang from one of its creators. [1]

2. Read Erlang and OTP in Action to learn more about the OTP (Open Telecom Platform), applications and gen_servers (which btw, you will find them all over).

3. Learn Elixir, perhaps from one of the books Elixir in Action [3] or Programming Elixir. [4]

4. Finally, start implementing your cool personal project.

Ah, one more thing: Elixir School is also a wonderful resource with tons of information and examples [5] and of course the official Elixir website with its excellent docs. [6]

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[1] https://www.amazon.com/Programming-Erlang-Concurrent-Pragmat...

[2] https://www.amazon.com/Erlang-OTP-Action-Martin-Logan/dp/193...

[3] https://www.amazon.com/Elixir-Action-Sa%C5%A1a-Juri-cacute/d...

[4] https://www.amazon.com/Programming-Elixir-1-6-Functional-Con...

[5] https://elixirschool.com/

[6] https://elixir-lang.org/

"OTP in Action" is an excellent book for learning OTP.

The following reading will take you a long way with Erlang:

Learn you some Erlang http://learnyousomeerlang.com/

OTP In Action http://www.amazon.com/Erlang-OTP-Action-Martin-Logan/dp/1933...

On Erlang, State and Crashes http://jlouisramblings.blogspot.com/2010/11/on-erlang-state-...

"Making reliable distributed systems in the presence of software errors" http://www.erlang.org/download/armstrong_thesis_2003.pdf

The last two links are "Erlang propaganda" describing the hows and whys of Erlang.

If you are considering writing any kind of fault tolerant distributed systems or frankly any client server system (In any language) I highly recommend reading the book "Erlang and OTP in Action." [1] It's a reasonably short read and will make you think through what needs to happen to build a robust system and get you to really understand and internalize the stuff that is talked about in this article in much greater detail.

The only downside is you might start to feel a bit dirty the next time you try to build anything with node.js, eventmachine, twisted or any of the other evented systems that are popular today.

[1] http://www.amazon.com/Erlang-OTP-Action-Martin-Logan/dp/1933...

I'm currently reading this Erlang and OTP in action http://www.amazon.com/Erlang-OTP-Action-Martin-Logan/dp/1933... and its pretty good so far, gets into the meat of Erlang quickly.