The Introduction chapters, then chapters from the Design and Implementation parts (depending on what your current focus is, one section might be more relevant than the other).

Copy/paste from the preface: "We recommend you start with Chapters 1 and 2, and then read the chapters that most interest you. Most chapters begin with a boxed preface or executive summary that outlines the following: • The problem statement • When in the software development lifecycle you should apply these principles and practices • The intersections of and/or tradeoffs between reliability and security to consider Within each chapter, topics are generally ordered from the most fundamental to the most sophisticated. We also call out deep dives and specialized subjects with an alligator icon."

(Book author here)