Hi,
I've made my Lua Quick Reference e-book a free download from 
https://orbitalquark.github.io/lua-quick-reference/Here's the summary:
Lua is a small, fast, powerful, and embeddable scripting language. It is 
well-suited for use in video games, application scripting, embedded 
devices, and nearly anywhere else a scripting language is needed. This 
quick reference contains a wealth of knowledge on how to program in and 
embed Lua, whether it is Lua 5.4, 5.3, 5.2, or 5.1. This book can even 
be used with LuaJIT, a Just-In-Time compiler for Lua based on Lua 5.1. 
Lua Quick Reference groups the language’s features and C API in a 
convenient and easy-to-use manner, while clearly marking the differences 
between Lua versions.
This book covers:
   -  Lua syntax, expressions, and statements
   -  Metatables and metamethods
   -  Object-oriented programming with Lua
   -  Creating and working with Lua and C Modules
   -  Lua’s standard library and its C API
   -  Collaborative multi-threading in Lua and C
   -  How to embed and use Lua within a host
   -  And much more
Cheers,
Mitchell