Web Services Explained - Solutions and Applications for the Real World by Joe Clabby - Prentice Hall 2002
An introductory primer suitable for less-technical managers, but with good coverage of what the technology is supposed to be for, issues and gotchas.
Developing Enterprise Web Services - An Architects Guide by Sandeep Chatterjee and James Webber - Prentice Hall 2004
Much more in depth and up to date coverage. I'm still reading it, more comments later.
