When it comes to business books there is a great deal of good books to pick from. To me the question is not: 'What is the best business book to read?', but rather 'which books can I not afford to miss?'.
I have found it tricky to decide, what really constitutes a business book. For instance Sun Tzu's the Art of War is an excellent book for business people to read, but it's really a military manual and not a business book. Ultimately I decided to go with a more narrow interpretation of what a business book is, in my selection.