Beginning Lua with World of Warcraft Add-ons is a published book by Paul Emmerich, the author of the 'Deadly Boss Mods' WoW AddOn, which aims to teach Lua and WoW programming for beginners though practical real-world exercises in WoW UI XML and the WoW Lua API.
From the publisher's web site:
Using the powerful Lua scripting language and XML, you'll learn how to build and update powerful mods that can fundamentally remake your World of Warcraft experience and introduce you to the field of professional software development.
- The publisher web site, Apress, contains downloadable real examples from the books, which on the page is currently a link to Apress github.
- World of Warcraft Programming - Another excellent published book resource
- UI beginner's guide
- UI FAQ/AddOn Author Resources