[amtap amazon:asin=0596529554]
A colleague recommended this book (link to amazon.com and amazon.de) to me and I was not disappointed. On the contrary, this was one of the most interesting IT books I have come across so far. The author is pretty well known in the SOA space and a regular speaker on conferences. He has a lot of real world experience and this shines through. What made the book particularly valuable to me, was that Josuttis points out when something is not black or white but gray and discusses the relevant aspects.
This book is probably not so easy to read for a beginner, but certainly of great value to the more experienced reader. It does not provide checklists or vendor recommendations but focuses on patterns and a good conceptual understanding. It will therefore not become outdated as quickly as many other publications but probably be relevant for a number of years to come.