Hundreds of intellectuals and artists are concerned about its implications for freedom of expression, while police, lawyers, and prosecutors consider it too imprecise.
There is a difference between collecting all copies of a book and burning them as a means of removing that book entirely and one person burning one copy of a book that they themselves own as form of protest.
I'm not sure which of the two you are referring to.
If the state or some public institution decides to burn all copies of To Kill A Mockingbird and deprives the public from the possibility to read it then it's censorship.
If you burn your own copy of To Kill A Mockingbird then it's not stopping anyone else from reading the book and you're effectively just burning your own money.