Kozak is the author of The Rabbi of 84th Street, a biography of Haskel Besser, which chronicles the Hasidic world of pre-World War II Poland, its destruction and its post-War rebirth. It was published by HarperCollins in 2004.
His second book, LeMay: The Life and Wars of General Curtis LeMay was released in 2009. In October 2010, he delivered the Exemplar keynote address at the United States Air Force Academy on the occasion of the selection of Curtis LeMay as the Exemplar of the Class of 2013. He has also lectured at West Point.