In November 2023, he released his first book, Ghosts of Honolulu: A Japanese Spy, a Japanese American Spy Hunter, and the Untold Story of Pearl Harbor , co-authored with former NCIS technical advisor Leon Carroll Jr..
Since his official departure from the long-running series in October 2021, Mark Harmon has transitioned into a new chapter of his career characterized by strategic production roles, literary ventures, and a selective return to the screen. In November 2023, he released his first book,
He continues to serve as an executive producer for the NCIS franchise and is the narrator for the prequel series, NCIS: Origins , which premiered in October 2024. In November 2023