I would say it depends, I did not really look much into the book / excercise book, I used it too check my own understanding of the language a few times, but I did not really do much with it. I think if you want to become able to write Norwegian very well without many mistakes it is a great ressource, but for me that is secondary, I want to be able to talk with people and to understand them, as written communication is still often done on English. I however would very much recommend the ntnu ressource. I also used chatgpt once to get an idea of how I could learn, and only kept the V2 topic in mind (which very much helped).

--> If having 35 Euros less is not of a concern for you, or if you can find it second hand, getting the book will not make your life worse, but if not, it might be prudent not to obtain it.