The Mediums' Book —Le Livre des Médiums, in French), is a book by Allan Kardec published in 1861, second of the five Fundamental Works of Spiritism — the philosophy Kardec had been publishing — being the tome in which the experimental and investigative features of the doctrine were presented, explained and taught.

In its pages one will find a classification of paranormal phenomena, with a special focus on those capable of communicating messages, and thorough descriptions of the mechanisms that — according to Spiritism — were involved.

This part first describes and categorises the kinds of phenomena that are related to spirits, like: Then it goes into explaining how to deal with the intelligent manifestations ("communications").

He thought it was wiser that the would-be medium knew what to expect and how to behave before he was given any instructions on how to engage on evocation.

There were, apparently, some cases of mania or personality disorder related to prolonged infatuation with Spiritism, which he was careful to advise how to avoid.