Well, if you can snag a copy of the Rich Jerk it can give you some insight into how to make money online. It's the best book, but it leaves out a lot of stuff for beginners. It's not going to tell you EVERYTHING about making money online, but it's a good book that can help you get started.
Basically you need:
A website
hosting
a decent layout
good content
ten hours to launch site
five hours a week to maintain site
And each week most people can make:
enough to buy a candy bar OR
enough for a few pizzas OR
enough to pay your bills OR
enough to quit a good job OR
enough for a nice trip to tokyo
And people DO click on adsense ads, some people make incredible amounts of money through adsense. How much do you think you get from someone clicking an ad? For some keywords it's like 5cents, for others it's about $35 PER CLICK. It's all about optimizing your site for the right keywords and writing Great related content. Google even gives you lots of good tips and guides on making the most with adsense, and it's free to join, so you have nothing to lose.