Have you considered that "the author is my friend" may have some information in it? For example, if Robert Reisch endorsed a book, you could reasonably conclude that Robert Reisch is the author's friend and that his friends tend to be liberals with a certain slant. It wouldn't signal the quality of the book, but it would help signal the content of the book.
I'd also add that some blurbs have high content, if the blurb is written by somebody with certain experitse,known tastes or strict standards. Ie, blurbs by book reviewers. Fabio > So a blurb doesn't signal "this is a good book" but rather "the author is my > friend." That is hardly reason to buy the book unless the purchaser also is > the author's friend. So blurbs ought not enhance book sales. Yet they > continue to exist. I take that to mean either the publishers or potential > customers are deluded about the nature or effects of blurbs. Another > possibility is that blurbs may serve some function besides selling books. > > So, why do book blurbs exist? > > John Samples > Cato Institute > >