You can purchase Joey Jacobson’s War at your local independent book store, or (in North America only) directly from Wilfrid Laurier University Press
You can also purchase it through Chapters Indigo in Canada, Barnes and Noble in the United States, or Amazon anywhere – for further details see https://www.wlupress.wlu.ca/Order-Books/General-Information
It has also just been released as an audio-book, read by Canadian actor Braden Wright.
The audio-book is available at audiobooks.com, audible.ca, and kobo.com.