It will save your startup. And no, I don't get a dime from your click but yes, I am going to buy 10 copies right now so I can have 3 in my bag to sell at cost to anyone that asks, wherever I go.
At first your goal is to define your assumptions, test them with potential customers and gather facts. Next integrate the facts into your product development. Continue verifying your product and business with customers, start your sales and go-to-market activities. Last, if you're successful, scale your company.
I read a lot business literature and Steve Blank's book is exceptional in way that it makes sense and offers you a path to walk on. For quick reference see http://www.slideshare.net/venturehacks/customer-development-... and http://steveblank.com/
Most of the existing product development literature fails to address the fact that most startups fail because they build something their customers don't want to buy.