How to understand the stock market
It made me
a smartypants 
"Frustrating but enlightening"
How I did it: I took Corporate Finance twice. To my great dismay I failed it the first time. But having a good overview and doing my homework really helped.
I don't think you can or should try to "understand" the stock market
without taking a university course. Otherwise you are going to be
getting the biases of the book authors that you read, and those who are
advising you.
Lessons & tips: Do your homework. You can't learn the right formulas in the right situations without practicing.
Resources: Probably any Continuing Education department of any university has courses. Textbooks are good.
