Web services require background in a lot of things and are not easy at all. It is very difficult to get just a book for complete begginers. I would suggest to read the J2EE Web services, of Monson-Hafael. Although it is outdated, IMHO it is a very good book, the background stuff are still valid. Read the chapters on SOAP WSDL and the introductory stuff to understand what is web-services. If you are interested in just the concepts and not do any coding this book is a good start.
For coding try to see if there is a framework that you think you can follow, and try to go into that.