Through many editions and translations of his three main works of sexuality (cited in this database) Mantagazza may have been the most widely read author on sexuality in the 19th century. He was also a widely published author on various other topics.
See V. Sigusch, "The birth of sexual medicine: Paolo Mantegazza as pioneer of sexual medicine in the 19th century," J. Sex. Med., 5, 217-222.
Digital facsimile of the 1875 second edition from Google Books at this link.