Important companion to The Book of Yokai!! Foster is still The Guy for yokai studies in the English-speaking world

For anyone interested in the folklore studies of Japan - this is the MUST-READ book.

A wealth of information for those interested in the history of yōkai. Unfortunately, this often reads like a PhD expanded into a book, with rambley tangents that, while often interesting in themselves, aren't that fun to read as a whole. Foster's at his best when the focus is clear, like in his in-depth critique of the Kuchi-sake-onna (slit-mouthed-woman) phenomena of the 70s. Like his subjects of analysis (the Japanese people), he categorises monsters and spirits into a comprehensible cultural history, and almost manages to move beyond this project into a less past-oriented terrain in the latter chapters... As it is, this is an interesting examination of folklore metamorphosing through the ages.