With 7+ Billion people on the planet most people have done something similar to any idea. Isn't the point in the book that you can still succeed by creating your own flavor of an idea or selling that idea to a new market?
Where does the actual advice start? This book is recommended pretty much every time someone asks a similar question, I might be willing to give it another shot if there's actual content somewhere in it.
Also, did this guy create a successful business outside of his self-help stuff before he started writing these books?
Prior to reading the book, I had a retire-early mindset. My idea was to work hard at high paying jobs and save a lot so I could retire early. After reading the book, I had the idea to create multiple streams of income in order to achieve the goal of retiring early.
Others have mentioned that it's not easy to find a lifestyle business that earns you enough income to live off of, and I've also had that problem. However, I've had partial success. I don't think I'd have ever pursued this path without reading 4HWW. It's not an instruction manual, though.