I liked the book ‘Elixir in Action’. It shows some of the language then immediately jumps into building a way too overcomplicated program (a distributed TODO list) that nicely shows off the features of elixir.

After that I just read some codebases. I find elixir codebases extraordinarily easy to read. The language does a great job of making ‘the good way’ also ‘the easy way’, and the linear nature of functional code is much clearer than the usual indirect dependency injected hell. Papercups is a fairly good starting point I think. I liked the livebook codebases too.