People still read Sun Tzu 2500 years later because its (1) not protected by copyright (2) easy to read and (3) free marketing since it's titled "The Art of War"

People still read Sun Tzu 2500 years later because its (1) not protected by copyright (2) easy to read and (3) free marketing since it's titled "The Art of War". At the very minimum, 10% of teenage boys of every generation are going to buy this thing. The reality is that most of it has a very "buy low, sell high" quality: generally obvious, but difficult to apply.