This is an essential part of marketing. If you get good reviews it can springboard into more and more people wanting to read what you have written. Contact experts in the field or genre of your book. Give out a few advance copies or send them a pdf of your work to review. When you get some good feedback, ask permission so that you can publish these favorable comments. It can even go in your book prior to publishing. Before your book is about to be launched, send it out for reviews. Gather all good reviews and send them in with your other book info. We will make them available on your Author Page on our website. They can be listed in a professional Press Release Sell Sheet that can be sent to bookstores, newspapers and other places that may want to do interviews with you or sell your book. We offer a Sell Sheet and full Media Kit. See this service for more details.
Some places that may review your book professionally are Publishers Weekly, Kirkus, and Foreword Reviews.
It can take 1 ½-3 months for some places to consider a book for review, and a good review is not guaranteed.