For a science fiction or fantasy novelist to have a book published with cover art by Michael Whelan could mean one of two things: either the book has been judged by the publisher to rank among such greats as Isaac Asimov and Anne McCaffrey, or the book is a miserable failure. What could explain this odd dichotomy? Whelan explained the phenomenon by quoting publisher George T. Delacorte, Jr., in the interview compendium The Sound of Wonder: Interviews from "The Science Fiction Radio Show."As Delacorte said, "What you do when you have a good painter, a good cover artist, is use him for your best books or your worst books. That way you cover all of your bases." In other words, excellent cover art accentuates a brilliant novel, but it can also save a publisher from losing too much money on a poor one. It is true, after...