Premium version is totally worth it, even though it's expensive, if you want the book instead of just a pdf. The standard version is pretty crappy, with thin pages and fragile binding, while the premium book is as you expect it to be. As for the content, the writing is not good. The rules could have been better written and more clear, as well as the layout and the chapters.
Apart from this, it's a great game. I love W20, and all awesome things to build great stories of.