Historian Steven Gillon was inspired by the popular TV drama “24— when he wrote his newest book, “The Kennedy Assassination — 24 Hours After: Lyndon B. Johnson’s Pivotal First Day as President.—

“Is there a way of taking some of the conventions of television and applying it to history in a way that is true to the historical material … but also to make it more interesting?— he asked himself.

It’s not the first time he has asked that question. Gillon, a professor of history at the University of Oklahoma, has been involved with the History Channel since before it came on the air, most recently becoming the channel’s resident historian about five years ago. His book is being released today, and Gillon worked as executive producer on the corresponding TV special that will air 9 p.m. Sunday.

Though hundreds of books have been written about President John F. Kennedy’s assassination, Gillon noted that most have focused on the question of who shot Kennedy. Because he chose to focus instead on the transition of power to Vice President Lyndon B. Johnson and only the first 24 hours that he was in office, Gillon could play up details that have been overlooked in previous accounts.

For example, Gillon focuses on the first hour after Kennedy was shot and the moment when Johnson understood that the president was dead. Gillon reveals how Kennedy aides’ lingering loyalty to the deceased president and suspicion of the elevated vice president kept them from clearly explaining to Johnson that he was running the country. Johnson, who had been riding in a limousine behind Kennedy and didn’t witness the actual shooting, was secluded in a room at the hospital, left to wonder whether Kennedy would live.

“At a time when the operating assumption was that the shooting was part of an international conspiracy, and that America’s national security could be at stake, it would seem imperative to guarantee a functioning chain of command,— Gillon wrote. “The obvious question is, Why did no one tell LBJ that JFK was dead or close to death?—

Gillon, who names then-Attorney General Robert F. Kennedy as his political hero, nevertheless blames the president’s brother for much of the rancor. Though the president had forced the two men to be civil, he was suddenly free to show his true contempt for Johnson after the assassination.

Kennedy’s staff felt the same way, despite the deference Johnson showed to a grieving Jackie Kennedy and the way he reached out to the president’s mother and immediate family.

He waited for the new widow instead of taking off without her, kept the bedroom on the plane private for her and offered her use of the White House as long as she needed it. Understanding the importance of her symbolic presence, he made sure to get her next to him in photos, most famously as he was sworn in on the plane. The unusual sensitivity that he showed to the Kennedy family and his laying the groundwork for his own agenda in the 24 hours following Kennedy’s death were “brilliant,— the author said. Gillon said the book’s positive take on Johnson took even him by surprise.

“I probably went into the book with a much more positive view of the people around President Kennedy and RFK and a fairly negative view of Lyndon Johnson,— he said.

Yet Gillon wrote that the way Johnson hesitated or made decisions out of fear of repercussions from the Kennedy family also plagued the rest of his presidency. Though he made great strides in Kennedy’s domestic policy after his death, it was Vietnam that defined his presidency.

“While confidently predicting victory in public, privately he feared defeat,— Gillon wrote. “Johnson fundamentally altered the nature of the war and dramatically enlarged America’s commitment to it. When challenged, he claimed that he was simply following the policies set by his predecessor.—

Gillon said he originally pitched this story as one of eight critical moments in presidential decision-making that would make up one book. His editor at Basic Books saw some of those eight ideas as worthy of their own books, though, so Gillon chose to write about the Kennedy-Johnson transition first. He hopes to write his next book about President Franklin D. Roosevelt’s reaction to the attack on Pearl Harbor in 1941.