Blurbs, the quoted testimonials of a book’s virtues by other authors, are now so ubiquitous, readers expect them, first-time authors stress about getting them, booksellers base orders on them. A blank back cover today would probably look like a production mistake. But while readers heft books in their hands and scrutinize the praise, it should be noted that blurbs are not ad copy written by some copywriter; they are ad copy written by a fellow author. “Ad copy” might be a bit harsh, but maybe not.