Lynda Girvan & Simon Girvan 
Agile From First Principles [PDF ebook] 

Agile principles and values transform the way organisations carry out business and respond to change. This book is an introductory guide to agile principles, values and mindset that will equip individuals and teams, regardless of role, to apply Agile from first principles. Practical examples are used throughout to illustrate agile theory with real-world context. This book is ideal for those wanting to achieve the BCS Foundation Certificate in Agile.