The original mass market books, dime novels made their debut in 1860. Writer's Almanac observes :
"Most dime novels were filled with crime, violence, and romance. They were mostly set in America during romanticized periods in the nation’s short history -- the Revolutionary War, the Civil War, or on the frontier. There were mistaken identities, villains, love stories, daring escapes, and sudden wealth. Outlaws like Jesse James and Buffalo Bill were heroes, women were swept off their feet by ne’er-do-wells, the life of frontier settlers seemed much more exciting than that of regular people stuck in nice towns, and violence was glorified. Dime novels were perceived as dangerous, especially for young people, on whom they might have a bad influence."
See the Library of Congress' Collection of Dime Novels here.