We know Dan Brown can sell books: His latest, The Lost Symbol, moved a million in a single day. But, it turns out, he can even sell other authors' titles. Ever since Lynne McTaggart's The Intention Experiment received a mention in Symbol, publisher Martha Levin says there's been a ''steady rise'' in sales for the self-help tome about noetics and the idea that the more people who share a thought, the likelier it is to come true. ''We're thrilled,'' she says. Behold the power of positive thinking.