More than a word actually. Too often writers are guilty of telling their friends and other writers about great reviews, but seldom take the time to thank the reviewer. We authors must do better.
Before I signed my first contract I'd been a reviewer. The truth is I recieved maybe 5 comments from the multitude of authors I did reviews for. When the thank you notes came through the review sites group, every reviewer was thrilled that they or someone else got a thank you from the author. That's how rare those emails are. After that review site closed the reviewers got together and founded of another review site. Again, we may recieve 10 responses from authors for the 40 reviews a month that we do. As reviewers we do get the occassional temper tantrum from an Author who believed they deserved a higher rating than they got.
Now why did I mention the thank you's and complaints - believe it or not a response on one review influences your next review. If a book is teetering on going up one level - a thank you from the author on the previous review might push it up. Throwing a fit to the reviewer could result in no reviewer taking your book. One more thing to remember - most reviewers aren't paid.
We must face that a good portion of our sales come not from our exhaustive and expensive promotion, but from those multitude of review sites that say something about our book. It takes two seconds after you read the review to either send an email or click the comment button. If it's a great review - thank them; if it's a not so great review - thank them and sincerely apologize that the book wasn't to their taste. That's it.
So Authors - remember to be kind to your reviewers. Good or bad they did take the time to read your book.