I originally wrote this as a comment on a message board, but decided to steal it back and post it here. The topic was how do authors deal with negative reviews.
The best reviews are those that teach us something about the book, that
have insight we didn't, that help us refine our own understanding or
that make us think about things we might not have thought about on our
own. (The worst reviews, generally, are those that only teach us
something about the reviewer.) So thoughtful, intelligent reviews --
whether positive or negative -- are useful, even if we don't agree with
them.
I don't often get to that goal in my own reviews; much of the time I just don't have the space. But it's what I strive for in my own writing and what I look for in the work of other critics.
If a review can make us think more deeply about a book, that's a good review.