This first edition was written for Lua 5.0. While still largely relevant for later versions, there are some differences.
The fourth edition targets Lua 5.3 and is available at Amazon and other bookstores.
By buying the book, you also help to support the Lua project.

3 – Expressions

Expressions denote values. Expressions in Lua include the numeric constants and string literals, variables, unary and binary operations, and function calls. Expressions can be also the unconventional function definitions and table constructors.