Book covers today are not the covers of even ten years ago, when it was reasonable to expect that nearly all potential readers would discover the book on a bookstore shelf. Now people discover books online. The covers they see are the size of postage stamps. We want a cover that works at that size—scans well when the potential reader is skimming a page full of covers—but also at actual size conveys the emotion and theme of the book.
[Coming soon: More on how I go about cover design work.]