BEIJING — In his 36th-floor hotel room overlooking Pyongyang, the North Korean capital, Merrill Newman developed a routine. He woke at 7:15, ate breakfast at 8 — eggs, toast and two cups of coffee — and then he waited.

A nurse and a doctor visited four times a day to take the temperature and blood pressure of the 85-year-old Californian. The interrogator, who sometimes shouted at him, called him a liar and told him to stop acting like a 3-year-old, came less frequently.

A year after he was released by North Korea, Mr. Newman, a Korean War veteran who ran afoul of the North Korean authorities on a trip there last year, has finally told the story of his detention in an e-book, “The Last P.O.W.” by Mike Chinoy, released this week.

A former United States Army intelligence officer who fought in the Korean War, Mr. Newman was detained by North Korea for more than a month and accused of war crimes.