As far as I read, the book is using an old version of Electron, so I don't know if by this point the author will going to explain auto-updates....
When you deploy an electron app, it will become a desktop application that is offline.

Now, if your main window or JS makes reference to external CDN resources, then yes, you need an internet connection to make those resources available.

My advice is: if you want a 100% offline electron app, make all the resources available in your project directory.
when you compile the application, it becomes a desktop application that can run offline.

and yes, it should. Electron can create apps without connecting to internet if it is desired.
Hello Steve

Probably you don't use electron on windows, but I found a very easy way to compile electron using gulp with a custom script instaaller.

Let me know if you want to know about it.