Erlang's process-oriented approach has given it a very different runtime environment. As Erlang and tools built on Erlang, like CouchDB, Riak, and EjabberD spread, understanding those underpinnings becomes much more important for people building and maintaining applications. This book will explore Erlang's unique approach to building a virtual machine, demonstrating how to take advantage of its power and tune it to fit your needs.
To be precise, it's not a review of "The ERLANG Run-Time System" - this book will probably never be published. This is a review of so-called "BEAM Book" - free e-book published online that continues the concept of the book mentioned above.
Additionally, this is not a proper, star-rated review - "BEAM book" is far from being finished. A lot of content is either just stubs or empty headers. My estimation (rough) is that only about 40% of expected content is in place. So didn't it make sense to wait with reviewing until the book is completed? TBH progress is slow, so no-one knows when (& if) it will happen.
OK, let's get to the actual content: book is worth reading even now, there are some very delicious details regarding ERTS & BEAM in general that are not that easy to find anywhere else. About how Erlang processes, stack & heap, how GC works, how does concurrency work (in detail - e.g. how do schedulers deal with process queues). There are some meaty details, e.g. about architectural decisions that have to be made to enable hot-code-reloading, etc.
My recommendation (for every Elixir/Erlang dev) is to get familiar with this one & keep checking it regularly for the new content.