Question

what is a best tone of a viewer of a book review

Answer 1

Ok, first let's understand what tone actually means. In the dictionary it says that "Tone is the way the author expresses his attitude through his writing." - YourDictonary 

So, the tone of a viewer of a book review would be....how they express the attitude through a book review! Then answer put the question this way. 

"Which is the best tone?"

Answer 2

Tone means the authors attitude, or the feeling the author wants the overall mood of the passage or book to be. So, probably a positive tone.