The ISO matter

I think the book doesn't explain ISO in a correct way. As far as I know, I learnt it in analogical Photography that ISO (Internartional Organitation for Standardization) started differencing a limited number of sensibility in the films.
That means ISO is not "real" in digital because there is no film. But the big advantage of digital is that you can change the ISO number whenever you want, however in analogical you have to finish the film you are using.

So, when the book said;

The best high-tech option (only available to digital shooters) for controlling the pictoral effects of both shutter sppeed and aperture is automated ISO selection (to date available on a limited number of professional models)

I guess it could be confuse for the readers. At least, it's for me.