Unpaid Traditional Book Reviews (Publicity): I already discussed how traditional book reviews are a fantastic form of publicity in an earlier thread I started on this site with the title Advertising vs. Publicity: Social Media Marketing for Authors. I encourage you to search for that thread and read it because it discusses the difference between advertising and publicity, and how authors can (and should!) use both to their advantage for best results.
Paid Online Book Reviews (Advertising): A faster and more certain way to have your book reviewed is by buying that review. If it's completed by a reputable company, it will still be an unbiased and respectable review. And one of the greatest advantages is that the approved review will be posted on that reviewer's high-traffic website for all to see which opens you up to an additional audience/readership you may not have had before. Another advantage is that many of these book review sites will attach a link to the e-commerce site where your book is sold directly beside the review.
Here's the disclaimer: these companies won't review crap. They will only review properly produced books. So, do yourself a favor and ensure you have your book properly edited/proofread and designed!
Here is a short list of reviewers you can purchase online reviews from:
- Foreword Reviews
- Kirkus Reviews
- Palmetto Review
- Pacific Book Review
- Penn Book Review
- The BookBag
- Hollywood Book Reviews
I'm sure there are many more, but this is a great start. Check them out and see for yourself. Some are more expensive than others, so you can choose the ones that best match your advertising budget.