This book is going to help developers using Lua with the opensource SpringRTS game engine. This book covers mostly the integration of SpringRTS with Lua. This integration takes place in the form of widgets, gadgets, mods, maps. All these elements can be created with the use of Lua and the inbuilt functions and variables that the Spring Engine provides.
It is assumed that the reader already has some basic knowledge of the Lua language. If you don't, then it is highly recommended that you first read the free Programming in Lua. A more fun way is by getting the source of widgets(which can be found here) and try to modify them and understand how they work.
Johan Hanssen Seferidis (aka Pithikos)