The history of erotica is best understood through the metaphor of archaeology. The texts, the various books and movies and still images and so forth we are familiar with, are the surface of a deep stack of layers of symbols and narratives accreted over centuries. In this process, the forms have changed repeatedly until they are distinct, but arranging them in the proper configuration, we see the evolutionary process.
Our guide on this dig is a literary and poetry critic named Harold Bloom. He explains that the relationship between different poems are either “weak misreadings”, which the poet tries in vain to get at what the earlier work was really about, or “strong misreadings,” in which the poet appropriates what he or she needs from the earlier work to pursue his or her own ideas. Bloom was discussing poetry, but this theory applies to other genres of literature, and particularly where there is less regulation from high culture, where texts mate rather promiscuously, like erotica.
I would argue that the bulk of what is categorized as erotica today can be traced back to two highly influential books, one from the early twentieth century, the other from the middle, both by women, both with women protagonists being initiated into exotic realms of pleasure, both widely dismissed as sensational, pornographic, misogynistic trash.