A lot of people I know speak very highly of this book. I disagree. It was so terrible I couldn't stomach finishing it. This is the early predecessor to the contemporary fantasy called "The Secret" - just think hard enough about what you want and it will happen. Sorry to burst your bubble, but that's bullshit. Regardless of what Napoleon Hill supposedly researched, desire alone is not a determinant of success.
Don't waste your time and energy on this book. Instead, go read "I Will Reach You To Be Rich" from Ramit Sethi for actionable advice on how to build your financial success, or "The Personal MBA" by Josh Kaufman for a real primer on how business works