I learned a lot of things from reviewing books. The most important, probably is that reviewing is not just a privilege but a burden as well. Every word in your review can make or break the reputation of a book. However, one shouldn't make reviews to just to please the author, that would be a bigger insult than if degrade their book. Though impartiality is advised and is often called for, a review is still a form of opinion and all opinions are biased. So what's a reviewer to do? My reviewer-sempai told me this, and I paraphrase, "Write a review as honestly as you can but in such a way that you don't insult the author." Ergo, there are always better ways of delivering unsavory news. Try to construct and reconstruct. The Thesaurus is a very handy tool in such a time.