There are many great free online resources for Lua including:
- A highly recommended detailed and authoritative introduction to all aspects of Lua programming by Lua's chief architect: Programming in Lua, by Roberto Ierusalimschy
- For an official definition of the Lua language, consult the Lua 5.1 Reference Manual, by R. Ierusalimschy, L. H. de Figueiredo, W. Celes.
- Lua Style Guide
- Learn Lua in 15 minutes
- Some options for linting