The book talks about the process of running a 5 day long test to validate your idea/product. You might have an idea to start new business or how to engage your existing customers, whatever it is you should do as quickly as possible and as effectively as possible.
The book provides a very detailed step by step guide how to run the full spring as well as explains why things are done the certain way.
While books tries to prove itself with examples from big or popular companies, it feel a bit cheap because success of the company doesn't depend on the success of the product. It's way more complex than that.
I'll be very interested to try it on practice. In theory it should work very well.