Ask HN: How did you learn about stock market/trading investing ? 16 years ago
http://www.amazon.com/Options-Futures-Other-Derivatives-5th/...
http://www.amazon.com/Investments-Zvi-Bodie/dp/007293414X
are both very good general resources.
Investments is a very broad approach that covers a lot of markets and basics and how things work. Very accessible to complete beginners.
The Hull is an introductory text and a great reference source to keep handy. You'll need to be slightly mathy to get it, but I suspect most HN readers will feel at home.