From time to time I see reviews on blogs of books that the reviewer didn't finish. Normally it isn't a good sign. My own position is that if I bought a with my own money book and I can write about why I didn't finish a book, why it didn't grip me. If I buy a book I also buy the right to say pretty much anything about it, or use it to line the parrot cage if I so desire.
But if a writer sends me a book I need to finish it. There's a sort of understanding. But boy do I feel bad when the review is negative. I know that's the deal, reviews must be honest. I know most authors realise this too.
If I am not going to review a book I toss it aside as soon as I lose interest; life is too short to spend it reading bad books. And given this attitude when I soldier through something I normally have a much more negative attitude by the end than I would at the 'giving up point'. And hence probably write a much more negative review albeit for more clearly thought out reasons.
I wonder what authors would prefer?
* Positive or nothing
* Give up and tell me why, or'
* Read on, maybe it will grow on you... (but the reverse is more likely, oh well).