LOS ANGELES — Anthony Zuiker, creator of the “CSI” police shows, is using Thursday’s episode of the flagship series in a unusual bid to promote his new crime novel and a Web movie with the same villain.

CBS, the most-watched network, approved Zuiker’s plan to write a “CSI” episode with the serial killer Sqweegel from his book “Dark Prophecy,” the author said in an interview. The episode features Ann-Margret as a wealthy Las Vegas woman with a past that the villain uses against her.

Zuiker, 42, decided to promote the book on the show when his first crime novel, “Level 26: Dark Origins,” didn’t sell as he’d hoped. U.S. book sales declined 1.8 percent last year to $23.9 billion, the Association of American Publishers said in April, with adult paperbacks shrinking 5.2 percent.

“If I can just get 1 percent of the 15 million people who watch ‘CSI’ to buy this book, I’ll have a bestseller on my hands,” said Zuiker, who calls the plan a “cyber-bridge” linking publishing, film and social networking.

“Dark Prophecy,” which will also be available on the iPad, is the second under a $2.1 million, three-book deal with Penguin’s Dutton unit, he said. The sum paid for co-author Duane Swierczynski and the cost of the movie, which was shot on CBS’s “CSI: New York” set in Studio City, Calif.

“We’ve seen characters move from TV show to TV show,” said Jeff Gomez, chief executive officer of Starlight Runner Entertainment, a N.Y.-based marketing company that specializes in migrating characters and stories from one medium to another. “But to move a character from a book to TV is really a significant way to extend a story line, and it comes from the book industry, which could use the help.”

“CSI: Crime Scene Investigation” has the ninth-largest prime-time audience through two weeks of the new TV season, according to Nielsen Co. data, with an average of 14.1 million viewers a night.