In Sep '08 I wrote that readers rate longer books as better, often ignoring opportunity cost, because they "spend so much time and energy reading the book that they come to believe it must have been good." Today the BPS Digest reports that "participants who'd experienced the sense of the time flying rated the task as far more enjoyable than did the participants who'd experienced the sense of time dragging." These two factors help to explain my pet theory about the success of the Harry Potter books.