I recently finished reading the E-Myth Revisited by Michael Gerber. This book is unbelievably great at breaking down the roles and responsibilities when starting a small business. But the best part is how to think about your business from the start, what you need to do, and how those pieces relate to each other. It gives a framework for any young business and how to grow to be successful.
This book is best for those thinking about starting a small business, or those just starting out. Or those struggling to grow to the next level of business. I like the "franchise model" it uses for how to think about your business. Essentially your small start-up business should be grown and run as if you're the first of a number of franchises. How will you turn it over to someone else so they can run and operate your business just as successfully as you do. That's the difference between a business and being self-employed: when you can step away and the company can still go.
This book is going on to my shelf for a re-read each year.