Speaking of Erlang resources, the legendary LYSE is a fabulous material well worth reading for Elixir users too. It’s in-depth, but written in very playful way. And to be honest, after a short while the Erlang syntax is fairly easy to read and write for any elixirista! https://learnyousomeerlang.com/

I would recommend the official elixir guide. The relevant chapters start with Introduction to Mix.

Not the whole guide is directly related to OTP only but I think it’s a very well thought through package you get.

I think this one is wonderful, probably the best course I’ve ever taken: Developing With Elixir and OTP Course | The Pragmatic Studio

The Pragmatic books are also wonderful, both the “basic” ones (Programming Elixir, Programming Phoenix), but especially if you want to dig even deeper with the advanced ones. See Pragprog.com q=elixir

Interestingly, Pragmatic Studio and Pragmatic Books have nothing in common, as far as I know. It’s just coincidence in names I think. And of course I keep confusing them and land on the “wrong” website every time I am looking for one of them

EDIT: oh and OF COURSE Sasa Jurcic’s Elixir in Action (2nd edition) is an absolute must have! Elixir in Action, Second Edition - Saša Jurić