Is this world all that exists, or are there one or more invisible dimensions in the universe that also harbor sentient beings? In The Astral Plane: Its Scenery, Inhabitants and Phenomena, esoterica expert C.W. Leadbeater brings together centuries of information about one much-hypothesized-about realm, the so-called astral plane. Whether you are a believer in unseen phenomenon or a skeptic, it makes for a fascinating read.