I find it interesting that knowledge that is ancient by its standards continuously gets rediscovered and repackaged in new form for a new generation. The Mythical Man-Month, for example, was a book whose essential parts were written in the early 1970s. Many of the observations in that book are quite similar to the Agile Manifesto discussed elsewhere in this book, except the message in the Agile Manifesto is adapted for a later era.
The Twelve-Factors App manifest was written by developers at Heroku, summarizing their findings from writing and deploying hundreds of applications. Some of the factors discussed in the manifest are timeless wisdom, some are more recent in development.
Let's go through the Twelve Factors and see how they relate to the book you are reading.
