The best way to learn is to start a business/become self employed.

A book would be: http://www.amazon.com/Ten-Day-MBA-Step-step-Mastering/dp/068...

Most are saying roughly the same thing (which I agree with)...If you're interested in working at startups, you'll learn more through your own startup. If you're interested in working at a big company, an MBA is worth more.

The only thing I'd add is that an MBA is to prove you've been taught certain things. Just because you don't go to school to learn them doesn't mean you can't go out and acquire the knowledge pretty cheaply (A good starting point is here: http://www.amazon.com/Ten-Day-MBA-Step-step-Mastering/dp/068...).

Between books and the wealth of business advice from proven successful people on the internet I'd think you could do better than an MBA if you try