At the time of this writing, the two topics arguably getting the most press, causing the most stir and generating the most buzz for web services aficionados are service-oriented architectures (SOA) for general audiences, and more specifically within Microsoft circles, Web Services Enhancements 2.0. Author Jeffrey Hasan (of whose work I'm a big fan, notably for his work in "Performance Tuning and Optimizing ASP.NET Applications" (http://www.apress.com/book/bookDisplay.html?bID=135)) paints a masterful picture of both topics in this outstanding work. This is a must-have if you've caught the WSE bug (pun accidentally intended) and need a practical guide to building better web services.
The material assumes a fair amount of .NET experience on the part of the developer, so the focus isn't on presenting exhaustive code examples and then describing them line by line; the intent is to give the seasoned .NET programmer a primer on how to make their apps more effective and more available to the rest of the world.
Using Microsoft .NET's associated technologies for XML Web services development, SOA is presented as being a maturation process for organizational web services, implementing a high level of abstraction, and therefore, a greater degree of universal appeal by promoting broad component reusability. WSE 2.0 is then tackled, diving into the major areas of consideration for SOAP messaging (security, encryption, routing, reliability, policy creation/enforcement etc.). Hasan describes the importance and role of SOA within large, disparate systems, preaching the gospel of interface-based systems and use of service agents (mid-tier objects managing communications between web services, business components and type/operation interfaces). This builds on the same concept discussed by Microsoft's Yasser Shohoud as a major building block for advanced web services development in his seminal book, "Real World XML Web Services" (http://www.awprofessional.com/articles/article.asp?p=30931).
Hasan also offers a refreshing, pragmatic discussion on the debatable misconception of the true "benefits" of loosely-coupled web services within enterprise-grade distributed applications, presenting a decent case for tight coupling in certain situations.
The book's prime example of an evolving stock quote service is appreciated a lot more than weak "Hello World" examples, and discrete enough to exhibit most of the advanced features of WSE 2.0 with a SOA slant. Although one of the prime tenets for WSE 2.0 is to facilitate web services in a transport-agnostic manner, many of the examples are geared toward SOAP messaging using HTTP, to the enjoyment of ASP.NET developers – something that's largely missing in the market today, with many current examples being WinForms apps. Desktop developers may grunt at the lack of representation in the book's examples for using other protocols (i.e., TCP, SMTP, etc.), but it's a minor price to pay.
Also, the book does sufficiently and consistently make mention of WSE 2.0 development for those of us not married to Visual Studio .NET environments, even though the preference of the author appears to prefer using the IDE.
This book is wonderfully written, using a voice that makes topics that can be quite difficult to wrap one's brain around easier to grasp. The chapters are very logically arranged. However, the book's major selling point is the working code and practicality of its theories, boasting a heavy dollop of both that experienced devs will appreciate and quickly put to use. With only a sparse amount of syntax-centric documentation, Microsoft Hands-On Labs, articles, and in-print books available at the moment for WSE 2.0 programming, this book is easily the leading resource for concepts and code today on the subject.
On that note, the chapter on the future of messaging with Indigo was an unexpected but welcome treat. I also found myself using the book's appendix more than I do most, which consists of a well-rounded collection of top platform-neutral papers on WS-* initiatives. Very nice touch.
This is an advanced book, but not so far out there that a developer with a few months of .ASMX work logged won't be able to pick it up without sacrificing their social lives and/or sanity. The book's writing style, arrangement of content and oft-brutal honesty (i.e., working with X.509 certificates in WSE 2.0 is pretty easy, but still far from completely painless; VS.NET's Add Web Reference option can royally screw up your proxy classes, et al.) make this a real winner and a great addition to your library.