Thanks for writing us about this, and I'm sorry for the confusion. Which book's files are you looking at?
Usually, the example files will be referenced in the book's text, so you can look at and work through the files along with the book. The files by themselves usually won't have much meaning, but they will make sense when following along with the book.
Hope that helps! Let us know what book you're working on, and we can give you more info.
I did eventually find out how to open them on the first tutorial page material. My mind was not thinking like that yet, I was thinking that there would be a more complete description in the Introduction section so I could start chapter 1 and know that the first tutorial would provide the open file information.
Thought you'd like to know for the next publication/update of manual.