Which American Idol judge is the dawg in bookstores? According to Nielsen BookScan, which tracks sales at 7,000-plus U.S. outlets, Simon Cowell's December hardcover memoir ''I Don't Mean to Be Rude, But...'' has outsold Randy Jackson's January paperback advice guide ''What's Up, Dawg?'' by 9 to 1. Why the upset? ''I have a more interesting life,'' Cowell crows. ''Some people love talking about themselves,'' Jackson retorts. ''I love helping people.''