Truce: The Day the Soldiers Stopped Fighting by Jim Murphy

From chapters.ca:
On July 29, 1914, the world's peace was shattered as the artillery of the Austro-Hungarian Empire began shelling the troops of the country to its south. What followed was like a row of falling dominoes as one European country after another rushed to war. Soon most of Europe was fighting in this calamitous war that could have been avoided. This was, of course, World War I. But who could have guessed that on December 25 the troops would openly defy their commanding officers by stopping the fighting and having a spontaneous celebration of Christmas with their "enemies?" In what can only be described as a miracle, this beautiful and heartrending narrative will remind everyone how brotherhood and love for one another reach far beyond the boundaries of war and politics.