The Mediums' Book is the second of the five books comprising the Codification of the Spiritist Doctrine. The book presents the teachings of the Spirits on all types of spirit manifestations, the ways of communicating with the invisible world, the different types of mediums, the development of mediumship, and the difficulties and obstacles that may be found in the practice of Spiritism. At the end of the book there is a helpful basic Spiritist glossary. Besides being a source of indispensable reading and research for Spiritists, The Mediums' Book is also an essential source of knowledge for any person interested in the mediumistic phenomenon, which is manifesting increasingly the world over, both inside and outside Spiritist activities per se. Since incarnates are an integral part of the exchange between the two planes of life- the physical and the spiritual- it is advisable that we fully understand the mechanics of such a relationship. The Mediums' Book is the safest guide for all those who have devoted themselves to communicating with the Spirit World.