Sadomasochism: Etiology and Treatment Book

I had read this as part of my LGBT Studies curriculum in college. But that was back in the late 1990's, and I wanted to read the updated version. Unfortunately, there didn't seem to have been much updating. The book is interesting more for a historical perspective on the beginnings of, or the classic ("old school"), leather community. However, I get the sense that the theories behind leather and kink practice have changed since their rise in popularity in recent gay life. I could be wrong. But, in any event, the book felt dated and somewhat obsolete. Having said that, the section with essays on the historical rise of the leather scene was certainly the highlight of the book.