A.J. MacKenzie is the pseudonym of Marilyn Livingstone and Morgen Witzel, a collaborative Anglo-Canadian husband-and-wife duo. Between them they have written more than twenty non-fiction books on subjects such as economic history and medieval warfare. They currently have two series of historical crime thrillers on the go. The first, set in 1790s Romney Marsh in Kent consists of The Body on the Doorstep, The Body in the Ice and The Body in the Boat (all published by Zaffre). The second, set during the War of 1812 between Canada and the U.S. consists of: The Ballad of John MacLea, The Hunt for the North Star, and Invasion (all published by Canelo).