The book addresses a modern reorientation of Lean, abandoning the classical waste dogma that brings direct efficiency gains and substituting by a way to achieving indirect efficiency in a continuous and sustainable manner. Waste is the output of a process that cannot be of further use, while value is a matter of valuation, a process whose output we conceive to be of further use. Value and waste are not antithetical, they are just not comparable issues. We achieve added value to the modern Lean Enterprise through synergies that bring sustainable economic benefits to the company. Such synergies use the complementarity theory developed by Milgrom and Roberts in 1990 on the principle that we can achieve maximal gains via the joint investment on complement activities and not investing. Complementarity is not something specific to Lean Enterprises; however, Lean Enterprises can benefit the most from such a concept. The reason is that Lean uses the principle of achieving more with less effort. Less effort does not mean the use of fewer resources, but the use of resources in a complementary way in order to achieve more, rather than using them. Complementarity is a feature by design. Complementarity by design will help modern Lean companies have an easier transition in the digital era and the new world of Industry 4.0. In this second edition, we have preserved the method of how to achieve Lean and have enhanced it to show how to move towards modern Lean within Industry 4.0 paradigm. However, if a company has not yet made the Lean step, there is no need to make that step first before yielding the benefits. Technology is the key. Modern Lean Enterprise strengthens out of the old paradigm into the new one of Industry 4.0. Because of evolution, such an enterprise achieves optimal technological complementarity necessary for synergies that sustain increasing profits.