When we write a book, we normally leave the Preface till the end, since we don't know what will be in the book until we're done. The Preface is partly an effort to pitch the book to a prospective reader, and partly an explanation of how the book came to be. You can read our current draft preface for "Network Security: A Systems Approach" in this week's newsletter: https://systemsapproach.org/2025/07/28/network-security-a-systems-approach/ 🧵 1/n