The main objective is to teach administration and configuration. Many books on Java EE technologies explain in detail how to use the technology, but then they often show you how to configure app server-specific configuration for only one or two app servers, and often go into little detail on that. Our book takes over where they leave off - we show you all (or most) of the configuration details for JBossAS.
Most chapters start with a high-level overview of the technology, followed by simple application (provided tutorial style), and then we use that application to highlight various configuration details specific to JBossAS. We always hit security. We often hit database configuration (if it applies). And we often hit high availability (or clustering).
We kind-of do both. For the most part, our chapters are structured so that the first 1-2 sections cover fundamentals, then the rest of the chapter builds on top of those fundamentals to give you either further detail, or a step-by-step walk through, depending on what makes more sense for the given topic.