The APEX (Achieving Performance Excellence) Initiative is a comprehensive business model developed by the National Institute of Corrections. The Initiative is an agency-driven systems approach that addresses organizational change and performance improvement in corrections. It includes best practices, data-driven decisionmaking using multiple self-assessment tools, and a Guidebook series with strategies, interventions, and pathways. This document is the introductory book in the Guidebook series that provides an overview of the series along with information on a large array of resources that address organizational change and performance improvement. The other books in the series that are mentioned in this book include Understanding Corrections through the APEX Lens; Achieving Performance Excellence; The Influence of Leadership on Organizational Performance; Applying the APEX Tools for Organizational Assessment; and APEX Resources Directory Volume 1 and Volume 2. The Guidebook series is intended to be used as a whole program or in parts to suit the needs of agency personnel. The Guidebooks and the tools in the Initiative can be used to create a customized implementation plan for individual agencies.