If Michael Dylan Foster's book reads much like a Doctoral dissertation, it is because it is based on his 2003 Doctoral dissertation: "Morphologies of Mystery: Ykai and Discourses of the Supernatural in Japan, 1666-1999". That noted, "Pandemonium and Parade" is in no way a watered-down version of its parent text. It includes further research conducted over the following seven years, along with a generous sampling of illustrations, both historical and current.
In addition to being an erudite and meticulously researched history of the ykai phenomenon in Japan, Dr. Foster is an excellent and engaging writer, who successfully conveys a deep love for his subject matter, while exploring in depth the cultural, psychological and fantastical elements of both the historical and present-day fascination these outlandish supernatural but all too earthly spirits hold over the consciousness of both the Japanese and students of folklore worldwide.
Dr. Foster's original Doctoral thesis has accompanied me on two visits to Japan; since its release, "Pandemonium and Parade" has been my companion on yet another, and is a volume I keep at close hand here at home, both for reference and for enjoyment of his literary style.
Anyone with an interest in ykai will find this a richly rewarding addition to their library, I cannot think of a finer work in English on the subject.