The advent of the Civil War impacted both the circulation of dime novels and their content. During the first few months of the War, dime novel sales declined. The novels ceased to be published twice monthly and appeared instead at more infrequent, extended intervals. As the War continued, however, sales increased, and batches of dime novels were delivered weekly to the Union and Confederate camps, where they were coveted among soldiers. Legend has it that when Union and Confederate picketmen met on the eve of battle, they exchanged their dime novels in a gentlemanly manner.
The War between the Union and the Confederacy was popularized in dime novels, as evidenced by The War Library, a publication devoted exclusively to Civil War stories. The heroes in these stories are typically steadfast soldiers whose allegiance to the Union is unquestioned. In "The Mysterious Major; or, Was He Blue or Gray?" the ambiguity surrounding the major's identity and military affiliation is the source of great anxiety and concern.