text:  and found that it led to a jump in sales, not just of the recommended book, but also of other books written by that same author. And interestingly, it didn't increase book sales. People didn't buy any more books. They just switched to buying the one Oprah recommended. And then I guess Craig really is a fan of Oprah. He wrote another paper about Oprah's endorsement of Senator Obama for president and estimates the impact that that had on his votes and contributions and voter turnout.