This has come up a couple times before. However, specifically for entrepreneurs, the books to read are:

  1) How to Win Friends and Influence People by Dale Carnegie
  2) Musashi's The Book of Five Rings
  3) Gonzo Marketing by Christopher Locke
  4) Getting Things Done by David Allen
  5) What Management Is by Joan Magretta

There are other books, but less relevant in a business context.