Eli Bendersky's website This book can easily fit into the "For dummies" series. It's really, really basic. The descriptions start with trivial examples (Joe and Bob start a company and invest 100$ each, etc...) and even a lot of comics-like drawings. Not sure for whom they are, perhaps for kids :-)
It's great if you want a basic understanding of how the stock market works, all the technical terms heard about it, and some trivial strategies for investing (you should buy when a rise of the stock starts, and sell as soon as a downturn begins, duh !!).
My first encounter with the topic was a few years ago, when I've read an article on the excellent How Stuff Works website. This book starts on the same level (that's 0), but is much more comprehensive. Stock options are explained, examples of how to read stock data in the papers are given, and it even goes into more complex things, like put and call options (on stuff like gold, goods, foreign currency, etc).
It's a very nice introduction to the subject, short (can be read in a day) and gives you a good ground. I have some other (more advanced) books I want to read about the stock market, and I feel that this book gave me a solid basis to understand the talk of this field.
On a final note: my feeling that the stock exchange is just one big casino got stronger after I've read about put and call options. I mean, what's that, if not gambling for the smart ?