A decade after the Nazis’ 1933 book burnings, the U.S. War Department and the publishing industry did the opposite, printing 120 million miniature, lightweight paperbacks for U.S. troops to carry in their pockets across Europe, North Africa and the Pacific.

The books were Armed Services Editions, printed by a coalition of publishers with funding from the government and shipped by the Army and Navy. The largest of them were only three-quarters of an inch thick—thin enough to fit in the pocket of a soldier’s pants. Soldiers...