Up until the publication of this book, the primary sources of Scrum reading have been the three books by Ken Schwaber – Agile Software Development with Scrum, Agile Project Management with Scrum and his latest The Enterprise and Scrum; and the excellent applied learning books by Mike Cohn – User Stories Applied, Agile Estimating and Planning, and Succeeding with Agile. (Yes, I know there are others) In Essential Scrum, Rubin has created a superset of all of these sources: it provides core Scrum definitions and explanations, nuanced implementations with applied learning, and scaled approaches for enterprise adoption. In addition, Rubin has created an entire new imagery to aid in visualizing the entire Scrum framework. Essential Scrum provides a comprehensiveness and cohesiveness that will enable me to recommend it as THE REFERENCE OF SCRUM.