First of all, authors put a lot of work into creating novels. So I wouldn't feel right about putting it down. I would be really upset if I put maybe years into writing a novel, only for it to be publicly shot down.
Books Are Different Things to Different People
You know when you see rave reviews of a book, then read it yourself and think what is all the fuss about? Or you love a book that no-one else seems to enjoy.
If I write a review saying I enjoyed a book and someone reads it and doesn't that's fine. If I were to read a book I didn't enjoy, that doesn't necessarily mean someone else won't enjoy it.
So if I was to give a bad review, and people decided not to read it because of that, how am I to know it wouldn't be something that may have enjoyed?
Did Not Finish
There haven't been many books I have added to my DNF list, I like to give a book a chance. So obviously I couldn't review a book I haven't finished, good or bad. If I haven't finished it, how do I know it didn't get really good in the second half or even last couple of chapters?
I haven't been at a point where I have had to give a negative review yet. If I have to review a book at some point I didn't like, you can guarantee I will try and put as many good points in as I can. I just don't see the point of going out of your way to put down someone's work.
I am really interested to hear people's opinions, do you write negative book reviews? Do you think I should? What are your views? Let me know in comments.