The opinions of others influence book buyers, and getting a buzz going often requires seeking reviews – but what if one is unfavorable? Book marketing services pros have some specific advice for you as the author about what to do and what to avoid doing. Before we get into specifics, it's vital to mention that writing is a business, and trying not to take a bad review too personally helps. Not everyone agrees nor likes the same thing, and some negative comments or reviews are an inevitable part of the process. Try to be thick-skinned about them and view them in the longer-term arc of success.
If you receive an unfavorable review, the first piece of advice is don't respond. Resist the urge to reply directly to an online review, and don't resort to posting comments on your social media complaining about it. It's unnecessary to defend any of your choices or decisions someone may criticize. You have your opinion, and they have theirs. Keep your eye on the big pictures and always write the best book possible and understand each reader will take it uniquely. There are (or will be) other more favorable reviews, and let them speak for your work. Avoid being a sore loser and complaining.
It's also helpful to keep in mind that many people are contrarian and may not agree with a reviewer's comments. The coverage a review gives your book will cause more people to find out more about it. With no coverage, discovering it is impossible for people, which is worse than suffering through a negative review. Publishing industry veterans also remind writers, especially first-time ones, that many of the most famous and enduring books received negative reviews initially. If your work is ahead of the curve, it may take time to sink in and make a more favorable impression.
There is seldom a need to over-correct in response to a review, but there may be things in one to keep in mind for future books. It's often wise to think them through a while after a negative review has been written because you're not in the right frame of mind shortly after. Even if the words were critical, there might be a way to turn them into something constructive. It also gives you an idea about where to seek reviews for future books. If a group of reviewers does not understand or appreciate your work, even if they are prominent, it might be wise to skip them in the future.