A grimoire is a textbook of magic. The term is used in a number of different ways, depending on one's stance on magic. Several museums, especially those with large rare book collections, have examples of grimoires on display, and modern grimoires can be purchased in many bookstores and from stores which specialize in magic and the supernatural.
The word “grimoire” comes from the Old French grammaire, a word derived from the Greek grammatikos, which means “pertaining to letters.” When most people were illiterate, the printed word was regarded as highly suspect and perhaps a bit supernatural. At one point, all books were referred to as grimoires, and over time, the world came to be used specifically for books which pertained to magic; during this period, the grimoire came to be associated specifically with evil.
The first grimoires appeared during the High Middle Ages, and they contained a variety of materials, from astrological calculations to directions for making talismans. Many grimoires also contained directions for spells, and many were specifically designed to help people summon angels or demons and perform divination. Many mystical texts were also treated as grimoires, and at one point, the Christian Church had a formidable collection of grimoires, thanks to its policy of confiscating such books from accused practitioners of magic.
In the modern era, the term “grimoire” is used in a number of ways. In communities where people believe in magic and actively practice it, a grimoire may be a generic term for a spellbook, or it may be used specifically to refer to a book which contains bad spells and dark magic. Some practitioners of magic consider grimoires to be like magical texts for demons and the forces of evil, and they would not use books which they classify as grimoires, while others view black magic as a potentially useful force, and choose to study such texts.
For people who do not necessarily believe in magic, the term could still be used to refer to a book of spells or other magical information which would be treated as an interesting curiosity, rather than a textbook. Many works of fantasy also include grimoires which are used by various characters for both good and evil, depending on the filmmaker or author's story. In these instances, a grimoire is often a heavily aged, very large book which may be embellished with fanciful designs and patterns to make it seem more mystical.