On his radio show and cable television programs, first on CNN Headline News and now on the Fox News Channel, Mr. Beck has enthusiastically endorsed dozens of novelists, a majority of them writing in the thriller genre. Mr. Beck, who now attracts 9 million weekly listeners on radio and 2.7 million daily viewers on television, often selects authors whose plots or characters reflect political stances that mirror his own. But he also promotes the work of authors who may disagree with many of his views. “He’s our Oprah,” said Brad Thor, a writer of political thrillers who has appeared on...