This work is one of the main texts crafted by FB Jevons; a relatively well known academic in his day, who managed to create, here, a work which would remain relevant after a century- it is a combination of strict religious history with linguistic anthropology; a fascinating field that most would benefit from studying at least in a basic sense.
This work is an excellent look at some of the christian conceptions of demonology from its era, in the roaring twenties. Based on field work in China and India, mostly by the author but referencing other missionaries as well, it purports to prove that demons exist, that evil is the agency of Satan, and that mesmerism and psychology play a role in possession.