Lua 5.1 Reference Manual

This is a short succinct reference manual written in a clear and concise manner. It tells you everything you really need to know and not much more. There are short examples of syntax to help explain the concepts. If you need to simply write programs in LUA, then this is your choice. If you need to go deeper (e.g. embed LUA in your own application) then I recommend you get "Programming in LUA".