The teens shift uncomfortably in their cramped wooden desks. Most are bored and hope the teacher will just get on with the lesson so they can get home already.

Bill O’Reilly, fresh out of Marist College and, at 21, barely older than the faces staring blankly his way, stands inside a classroom at Monsignor Edward Pace High School in 1970 and realizes he has a challenge — how to teach history to a preoccupied audience and make it interesting.

O’Reilly’s revelation: bring the historical characters alive as real people.

“The kids were not motivated, so I did it in a way that was fun,” says the host of Fox News’ top-rated The O’Reilly Factor, who appears Saturday at Miami Book Fair International, from his office in New York City. In just a few hours he tapes that day’s O’Reilly Factor, a news commentary program that routinely trounces the cable competition.

O’Reilly, 63, commands attention. Some would say the former Catholic-school boy is a firebrand for his predominantly conservative political views. Some would offer descriptions that are more unkind. For O’Reilly, everything started back in that Monsignor Pace classroom in Opa-locka, some 40-plus years ago.

“I got the blood and gore out there, and the personality profiles of who they were,” O’Reilly says of his approach to teaching history. “I made them real people so, in the back of my mind, that was a way to get people involved. When I became an author and did successful books on contemporary problems on what was happening in the country, to the dismay of my publisher, I said I was going into history books, and I used the same techniques I used in the classroom in Pace. I was fortunate to find Martin Dugard, a brilliant historian.” Their biographies, he says, are “fun to read.”

Indeed, their two history books — Killing Kennedy: The End of Camelot (Holt, $28) and last year’s Killing Lincoln: The Shocking Assassination That Changed America Forever — crackle with the tension of a brisk James Bond thriller. Yet they aren’t novels, a point O’Reilly wishes to enforce.

“Some people get confused, but these are nonfiction books and they are well researched,” he says. “These are not Gore Vidal.”

This week, both books are performing like the latest bestsellers from John Grisham or J.K. Rowling. Killing Kennedy is No. 1 in its fourth week atop the New York Times bestsellers list; Killing Lincoln sits at No. 3 in its 57th week.

O’Reilly’s style is not the norm for historians, says Florida International University history professor Darden Pyron, author of biographies on Gone With the Wind scribe Margaret Mitchell and musician Liberace.

“Most historians are not interested in telling stories. When I was writing the Margaret Mitchell book and discussing with colleagues that I wasn’t sure what the plot is, a silence fell across the room,” Pyron says. “Without doing damage to the data, the first responsibility of a professional historian is to get the data straight, not to tell a story. To engage an audience . . . . storytelling is essential, but historians don’t do it. If more than 300 people read what I write I assume I’m doing something wrong.”