This blog entry tells what’s wrong with a lot of SEO — search-engine optimization — advice. Why should a book-writer care? Because whether you are just interested in promoting your book, or your book is part of a larger marketing strategy, “organic” (that is, non-paid) search-engine results are important to you.
In other words, when someone googles some of your keywords, you want your site to appear at the the top of the search results. That is what SEO is about, and what SEO consultants offer. The above-referenced blog entry tells you what to beware of.