The following books are excellent resources that go into far more detail than I have room for here. Each has a different focus, so they complement each other nicely.

Agile Software Development [Cockburn] focuses on the “individuals and interactions” aspect of agile development. Most of his thoughts correspond to the principles I outline in Chapter 12.

Lean Software Development: An Agile Toolkit for Software Development Managers [Poppendieck & Poppendieck] applies concepts from Lean Manufacturing to agile development, with emphasis on the principles that I describe in Chapter 13 and Chapter 14.

Agile Management for Software Engineering [Anderson 2003] is a bit dense, but it has detailed coverage of the Theory of Constraints, which I discuss in Pursue Throughput” in Chapter 13.

Practices of an Agile Developer [Subramaniam & Hunt] is an easy-to-read collection of guidelines and advice for agile developers, similar to what I discuss in Chapter 15.

Agile Software Development Ecosystems [Highsmith] looks at several agile methods through the lens of people and principles. Read this if you want to understand agile development in depth.

Extreme Programming Explained [Beck 1999], [Beck 2004] discusses the thought process behind XP. It will give you more insight into how agile principles relate to the XP practices. Try to get both editions, if you can; they describe the same basic process from very different perspectives. Studying both books and looking for the underlying commonalities will teach you a lot about agile values and principles.