The book explains how to use the ASP.NET AJAX features to create richer, more responsive dynamic web sites. It explains the architecture, including the ASP.NET server elements and the client-side Javascript library and runtime, and it walks the user through examples for each feature element demonstrating how the client and server interact to produce a better web application. In addition to acting as a reference for the feature set, it progresses in a way that educates the user about the need for AJAX features and how the pieces of ASP.NET and AJAX build on each other to provide a comprehensive framework for rich application development.