The Erlang Runtime System is a fantastic resource for understanding the BEAM itself. It’s focused on erlang but it applies equally to Elixir.

Not that I know of, though I hope to be proven wrong!

There are really 3 aspects of Elixir’s “implementation” you might be interested in:

1. The underlying BEAM virtual machine used in both erlang and Elixir:

   • The erlang blog has some great posts about this, ex this article.
   • The BEAM book already posted is also great!

2. The erlang-implemented compiler for Elixir, and Elixir’s AST:

   • There’s actually… not a lot out there on this. I’ve had to read through, and even tinker with, the compiler before, but there are scarce few resources. That’s reasonable since it’s sort of a private API, but I know I would have loved more resources!

3. The standard library and related design decisions:

   • The Elixir blog has some good articles; these days it’s mostly release announcements and case studies, but a few of the earlier ones dig into this a little, ex this article.

   • It’s far more dialectic than a cohesive presentation of anything, but there’s a decade of language design discussion on the core mailing list. You can search just about anything Elixir and see how it blossomed into being.

Other resources of note:

• A great crash course to OTP (which is the sort of erlang stdlib/framework for concurrency) for Elixirists is Designing Elixir Systems with OTP.
• Learn You Some Erlang is an introduction to erlang itself, but also dives into OTP a bunch.
• Also by Fred Hébert, Erlang in Anger is a great resource for debugging and fine-tuning your running systems.