The fourth book is about failure. It’s what happens when a system behaves differently from how we expected it to, with adverse consequences for those who were relying on the success of that system. Failure is often as much about misunderstanding how a system works, as it is about the lack of effort or plan to bring the system into a successful configuration.

Almost nothing humans build ever works on the first try. Failure is part of almost any successful endeavor, whether it’s an engineer trying to build a successful rocket engine, a CEO trying to build a successful organization, or a scientist trying
to discover a new mathematical formalism that accurately describes some phenomena.

This book will cover three primary facets of failure: How to avoid it, how to recover from it, and how to learn from it. 

The worst failures of all are the kind that you can neither recover nor learn from. The ones that put a permanent end to your attempts at solving the problem you are aiming to solve. This book puts a special emphasis on that kind of failure.