Answer by Matthew Spencer:
Not specifically a genre, but a publishing model that supported many different genres. These included, but were not limited to, science fiction, horror, romance, westerns, adventure stories– in other words, the same mass market categories we see in contemporary fiction.
The pulp in pulp fiction refers to cheap paper that was developed in the late 19th century. That, along with more efficient printing techniques, made books and magazines more accessible to mass audiences. This in turn supported the growth of writers and publishers catering to popular tastes.
The terms dime novel and penny dreadful refer not only the cheap cost of these publications but also the overall quality of the writing. Pulp fiction was created and published on an industrial scale with little thought given to careful composition or literary taste. A single author working alone could churn out hundreds of stories or a dozen or more novels a year.
Though most pulp authors are now justifiably forgotten, there were aspects of the industry that encouraged artistic innovation, especially in fantastic or speculative literature. H.P. Lovecraft and Robert E. Howard, creator of Conan the Barbarian, are two prime examples of authors who worked within the pulp world and are still widely read today.
Then as now, publishers printed violent and, for the time, highly sexual content in order to boost sales. And also like today, educators, politicians and activists worried about the effect that reading these stories would have on children, particularly young boys. In the 50s, violent content from publishers such as EC Comics ignited a public reaction that led to the creation of the Comics Code, an important early example of a general rating system.
During the 50 and 60s, the trade in pulp fiction went partially underground, with more and more sensational subject matter. Magazines with stories catering to nudists, mercenaries, drug enthusiasts, beatniks and hippies, among other specialized demographics, appeared.
With the revolution in digital publishing and the migration of print into the prestige market, the term pulp is not completely accurate in describing the physical format of books and magazines, but aspects this publishing model do still exist today. Electronic publishing has lowered overhead costs and scheduling restrictions to such an extent that we might be seeing a contemporary renaissance in pulp fiction