The Spirits' Book is a foundational text of Spiritism, written by Allan Kardec and first published in 1857. It consists of a series of questions and answers that explore the nature of spirits, the afterlife, and moral principles. The book aims to provide insights into the spiritual world and the relationship between humans and spirits. The work is divided into four main parts: the nature of spirits, the moral laws governing their actions, the future of humanity, and the practical applications of Spiritism. The Spirits' Book serves as a guide for understanding spiritual phenomena and encourages personal growth through moral development.