I bought the book
Lua with World of Warcraft (ISBN 978-1-4302-2371-9), and although it is also targetted against WoTLK (I bought it back in 2009), it is a good entry point for learning how to make addons.
It explains the general flow with events and the UI setup (which basically is the same as Vanilla).
When it comes to how to use the events, then the Internet is the only source; the book is not of much help here really. Especially
http://wowprogramming.com/docs/api_categories is a nice source of information for all versions of WoW.