This paper studies the economic effects of endorsements. In the publishing sector, endorsements from the Oprah Winfrey Book Club are found to be a business stealing form of advertising that raises title level sales without increasing the market size. The endorsements decrease aggregate adult fiction sales; likely as a result of the endorsed books being more difficult than those that otherwise would have been purchased. Economically meaningful sales increases are also found for non-endorsed titles by endorsed authors. These spillover demand estimates demonstrate a broad range of benefits from advertising for firms operating in a multiproduct brand setting.