If you’re a developer with an interest in Erlang, the Erlang Handbook will give you a quick overview over its main concepts. If you’re already into Erlang, then this will be your dirty little helper whenever you need to freshen up on something.
The Erlang Handbook is a quick reference guide shorter than 50 pages, created by Bjarne Däcker and Robert Viding. It is a “live book”, which means that it is open for community editing and contributions. More information can be found at: http://opensource.erlang-solutions.com/erlang-handbook/