Here's another book I'm ashamed to say that I never got around to reading, despite my background in military history. And from that military history perspective, I found much of the advice interesting and worthwhile, especially all of the permutations of when to fight and how.
But "The Art of War" has gotten more press in recent decades as a business book, which is the category it's listed under on the dust jacket of my copy. From this perspective, however, I found little to recommend it. Perhaps the "capitalist warrior" model made more sense in the 80s when this book was so popular (the great line from "Wall Street" in which Gordon Gekko say "greed is good"), but in the "flat earth" internet age of instant information, this "us vs. them" with the use of "spies" and iron discipline being the main means to success seems misguided if not downright inappropriate for much of our contemporary business context.
On the other hand, the most famous line from the book, about knowing both yourself and your enemy, is one of those universal truths that seems obvious in hindsight but was probably novel and inspiration when this work was first put together over a couple thousand years ago.
Bottom line, an obvious classic, especially for military matters, but I personally didn't find as much to use in my leadership role as I did from reading "The Prince."