I've seen Sun Tzu's The Art of War recommendations in enough business books that I figured I should finally go ahead and read it. Written some 2,000 years ago, the book is literally about how to command an army in order to win battles. But it is often argued that the concepts apply also to businesses in competition.
There are undoubtedly some concepts that apply. For instance, Sun Tzu recommends keeping your opponent off-guard by doing what is unexpected. He also argues that one should attack where the enemy is weakest, and then keep going towards the weakest points.
But then there are points where I was a little lost. For example, Sun Tzu says you always want to fight from the sunny side of the mountain. Since I don't plan on actually engaging in hand-to-hand combat any time soon (at least until earnings season is over), I wasn't sure what to make of most of the book. I'm not the smartest guy at abstracting concepts from one field into another, so it's probably best that I stick to books that make these connections explicit for me.
I think there's also a chance a lot of books will abstract concepts from The Art of War a little too far. If you try hard enough, you can massage any concept in one field such that you can force-fit it into another, but that doesn't mean it's a good idea to do so.
Of course, this is also one of the most talked-about books of all-time, so don't not read it on account of my only luke-warm review!