This is a very classic book on military strategy -- and some might say, strategic thinking.
Whereas Machiavelli's book is written for a statesman, Sun Tzu's book is written for a general responsible for military campaigns and engagements.
However, the book's claim for fame is its alleged inspiration to modern-day corporate managers in their marketplace battles and rivalry over customers' patronage.
Was it good?
Actually, I would say that the book was not very good.
Of course it must be understood that the book originally was written some 2500 years ago, and therefore one can't judge it by the standards of today. I recognize this, and mainly refer to the alleged relevance for modern-day corporate strategic management, which I see as pretty slim.
Admittedly, the book contains insightful statements with quite universal applicability, but the problem for me is that such statements are so obvious that one most probably learns very little from them. For example:
"So it is said that if you know your enemies and know yourself, you will not be put at risk even if you have a hundred battles.
If you only know yourself, but not your opponent, you may win or may lose.
If you know neither yourself nor your enemy, you will always endanger yourself." (Chapter 3)
And when the bulk of the 'wisdom' is -- in my opinion -- like this, I really can't see how the book should reside at the bedside of corporate strategists.
The main take-away for me?
I have to grant to Sun Tzu that thinking on competitive strategy has flourished already some 2500 years ago. In this sense, the forefront of strategic management scholarship can be said to be "a series of footnotes to Sun Tzu" (c.f. "The safest generalization of the European philosophical tradition is that it consists of a series of footnotes to Plato" by Alfred North Whitehead).
Who should read the book?
I think that everyone who has heard or read the book as being recommended as a reader in modern-day strategic management should read the book and see for him-/herself whether there is anything there for him-/herself.
The book on Amazon.com: The Art of War