It is nearly impossible to write a book that is both mathematically rigorous and sufficiently down to earth to be accessible to the professional trader. This book is a step in the right direction. It maintains the mathematical accuracy and depth without bogging the reader down with technical derivation of formulae. At the same time, it is written by a trader whose experience in the real market compels him to constantly question the 'nice' assumptions used to derive these formulae.
Taleb is first a market practitioner who uses models and pricing formulae to enhance trading and not the other way around. If there is a discrepancy between theory and reality he doesn't blame the markets.
The book is very personal and leaves no doubt what the author's opinion is on VAR, continuous hedging and other sacred cows of modern finance. The debacle in the financial markets in 1998 and the apologetic excuses by famous traders and theoreticians indicates that there is more than a grain of truth in Taleb's skepticism.
The importance of this book is that whether one agrees or disagrees with Taleb, it forces the reader to question his basic assumptions and rethink common truths. The book is unique: it is stylish, philosophical, literary, and if one may say so of a hardcore financial book - it is very entertaining.