When coding the first example in this book it didn't work for me. But I did get it to work by using a bit different way than what the book suggests.
After you install Web Matrix, when creating the first site be sure to create a new site from a template gallery. I picked Empty Site under the Templates area. This takes care of any IIS quirks starting with a usual website you might find.
After the website is created, I deleted the deafult CSHTML file. From here, I followed the directions in the book. Whenever you click "run" it appears that the WebMatrix software does not load the web page you are working on, it loads the root file which is either Default.cshtml or index.cshtml