On the iPhone (7 Plus) using Safari, I select “Add to Home Screen”. When I open the icon, it only contains the books/chapters that I view before I turn off the WiFi.
It works well on Windows with Chrome. When I try iPhone w/ Chrome, the option for “Add to Home Screen” is not available.
With the current PWA, the device has to downloads all the chapters before it is really a PWA. This can take some time even on a good internet connection. Unfortunately, there is no visual indication that it is ready. This is one of the reasons that we are re-writing the PWA.