A groundbreaking (and taboo
-breaking) work in sexology
, Professor Richard von Krafft-Ebing
's Psychopathia Sexualis
) is a series of case studies
of various kinds of "sexual perversion
While the subtitle makes it clear that the good Professor intended this as "a clinical-forensic study", and although his writing is moralistic, the modern reader is likely to find this a source of wonder at the infinite diversity in infinite combinations within human sexuality.
Serious collectors can still find the German original first edition for under $1000. Most sane readers, however, will prefer the English-language 1999 reissue for under $20.