I just put online at scribd.com Leoline L. Wright's occult novel "The Jewel of Atlantis," serialized in "Theosophical Forum." Its a pretty good book, with a black magician, a South American Adept, and a case of obsession. (link)
I haven't read it for a few years, but there is a newspaper reporter, a woman love-interest - the woman is given a very unusual gem which she becomes infatuated with - her personality undergoes a drastic change for the worse - it is surmised that it has something to do with the gem - the reporter goes on an occult search for a way or someone who can find a cure for the woman's obsession by the entity that is associated with the gem..... etc., etc., Supposedly a big publisher wanted to publish the book, but Wright refused to "sex it up" as they required, ha! (That's what George LeGros told me.)