Christopher Dummitt, Unbuttoned: A History of Mackenzie King's Secret Life (McGill-Queen’s University Press)
E.A. Heaman, Tax, Order, and Good Government: A New Political History of Canada, 1867-1917 (McGill-Queen’s University Press)
Adam Montgomery, The Invisible Injured: Psychological Trauma in the Canadian Military from the First World War to Afghanistan (McGill-Queen’s University Press)
Cheryl Suzack, Indigenous Women's Writing and the Cultural Study of Law (University of Toronto Press)
Donald G. Wetherell, Wildlife, Land, and People: A Century of Change in Prairie Canada (McGill-Queen’s University Press)
I hear rumours about the shortlist for the J.W. Dafoe Prize for Biography -- but nothing up on its website for 2018 yet.
Update, April 20: Tim Cook won the Dafoe 2018 for Vimy. Deets here. Never did see a shortlist.