As a PhD student in Economics interested in financial markets I have read NN Taleb's book (The Black Swan), then Riccardo Rebonato's (Plight of the Fortune Tellers: Why We Need to Manage Financial Risk Differently, 2007) and Benoit Mandelbrot's ((Mis)behaviour of Markets: A Fractal View of Risk, Ruin and Reward, 2005). All books contain the same message: the assumptions underlying modern risk management models are wrong (and yes, this has something to do with the financial crisis). All books are worth reading, but if you know one, you know the others. Which leaves you with the question of which book to read.
Here is my recommendation: For economists and people with a mathematical background, I would suggest Mandelbrot. The story is very nice, and his explanations original. He was the first to suggest that stock prices resemble fractals, and not random walks. Since he had a co-author, the book is a good read, given some prior knowledge. For those without some intermediate knowledge of Economics or mathematics or both, I would suggest Riccardo Rebonato's book. It has a clear structure and is easy to understand. Still, it does the job and gets the point across. Now, for those who think they know a bit of philosophy, economics, mathematics and the universe in general, it's "The Black Swan" that I would recommend. Taleb is getting at the subject from a philosophical point of view, of course based on mathematics, and the story unfolds in a hilarious way. Taleb is smart and has a lot of knowledge of things that matter and things that don't. It's funny to see him bark at different groups of scientists (economists, philosophers,..). I have found no instance where his disappointment at people/theories is misplaced. Being outside the scientific establishment has its advantages.