Ok, I think I figured it out. I'll post it here for anyone else who stumbles upon this thread and has the same problem.
In Chapter 5 of the book, on page 92, they create a custom model called "kb". You need this model in order for the kb-create.get.js
file to run correctly. Here's what you need to do:
1) Download and unzip the zip file of all of the examples for this book from wrox.com (link:http://www.wrox.com/WileyCDA/WroxTit...-DOWNLOAD.html
2) In the Chapter 5 folder, find the file called "kbModel.xml". Open it up and copy its contents.
3) In Alfresco Explorer, under "/Company Home/Data Dictionary/Models" create a new XML file called "kbModel.xml". When you're creating the content, make sure Type is "Content" and Content Type is "XML" (for the two drop downs).
4) Follow the instructions on page 78 of the book to activate the model.
Once this is done, you should be able to run the Web Script and have it work.
Hope this helps.