My reference for SOAs is currently :

Entreprise SOAs : Service-Oriented Architecture Best Practices - D.Krafzig, Karl Banke, Dirk Slama.

I'm a bit surprised : although those 3 guys are German they didn't realise that Software AG is a highly qualitative player in supplying tools for an SOA. EntireX and Tamino have won awards at the Web Services Journal as best platform for web services (see here Software AG sweeps the board for Web services at the ?Oscars of the Software Industry )...

I understand that US books don't speack about German software, but what about the German ones ?