There are times when a book blog helps make your Kindle book more noticeable, and there are times when an author blog helps bring more attention to your book. This article on how blogging can help you dominate your niche is an excellent introduction to this concept.
My own experience is that this practice has helped my free bookselling blog hosted by Blogger (http://sellusedbooksonline.blogspot.com) land at the top of both Google and Bing search results for a variety of keyword phrases -- and especially for one I carefully targeted: "work from home selling used books." The last time I checked, that blog showed up in the #1 spot out of 127 million website results as that keyword phrase is typed into the search box on Bing.com.
Here's the screenshot of how it showed up on the first page of Bing.com results:
What's more, by adding my author profile to my posts, my photo shows up in the search results; as you can see, it's one of very few images that show up in results and I think it helps draw the eye to this post.
On the Google.com results page, my blog ranked #5 out of 811 million returned results. In my book, showing up anywhere on the first page of Google is a homerun.
This strategy works. When a visitor clicks on the title and winds up on the blog page, the article shows in the left column and my book cover shows in the right column. If the reader is curious to learn more, and he or she wants to check out a free sample chapter (Amazon always offers a "Free Look Inside" feature right at the top of every book's thumbnail image, giving readers a short sample of the book they are considering buying) then all they have to do is click on the book cover and they are automatically whisked to the Amazon sales page.
I'd highly recommend reading and heeding the advice in this article at http://thefutureofink.com/book-blog/, which lays out the reasons behind this and the best way to set up your blog. Worth a careful read.