N-Tier Architectures have been well known for a while but very few books focus on application servers. Application servers typically occupy a new physical third tier between the client and server, although it could be a logical division.
This book covers application servers from three different perspectives; architecture, design and programming. Clearly whole books have been devoted to each of these subjects so the material is not in depth. However, for novices or those who have focused on traditional (2-tier) client server development this book offers a useful overview. Those requiring more in depth coverage can follow-up by using the references and further reading that accompany each chapter.
The text is clear and well laid out with good explanations. The examples use UML and Java, although they are only illustrative they do cover the key points. There is sufficient guidance that it is possible to take the example and produce a working (simple loan calculator) application server. The real benefit to this book is the overview of many related subjects and tying those into the common thread and in essence providing the foundation for understanding how to build an application server and what needs to be considered.
In short this is a useful overview for those with either no experience or very little experience in n-tier application development. Its main value is in providing a useful overview of the many related subjects. For those who have had their fingers burnt in this area this book will not provide any new insights although the references and further reading might.