Holy book

Holy Books were objects that priests and other divine spellcasters could use to learn new spells. Despite the denomination, holy books were not necessarily books per se but could take unusual forms such as magically floating bronze scales, a thick everbright chain, or a crystal ball. The term was also sometimes used as a catchall for religious books, such as canons.

Description
In their most usual form, holy books were tomes containing a collection of prayers and rituals dedicated to a specific deity. Those prayers could be used to learn new divine spells, but that privilege was usually reserved those faithful to that deity. A typical holy book could teach around 10 to 20 spells.

The most common of holy books were called temple tomes, because they were jealously guarded in holy temples. Temple tomes were usually stored in highly protected vaults or hidden chambers, and some clergies went as far as displaying replicas on elevated reliquaries for their flocks to admire.

Holy books were crafted with lots of care. Some were made of rare and expensive materials, such as the hide of exotic beasts, in order to impress the devout. Others were built with durability in mind, using methods such as stamping words on everbright metal pages.

Powers
Typical holy books didn't magically affect individuals who simply read them or shifted their pages (as opposed to magical books such as the Book of Vile Darkness ). It was however a common occurrence for those books to be protected by glyphs of warding unleashing magical defenses against creature of the wrong alignment, race, or even temple rank. Such glyphs were carefully crafted by the churches with divine approval, and were hidden alongside various symbols, holy runes, and "dummy" glyphs designed to waste the spells and time of intruders.

Because of the divine permission granted by deities, holy books could be used by priests of the corresponding faith to learn spells outside the spheres normally available to them.

Content
The exact content of holy books could vary slightly, but they were usually organized as follow:
 * An opening prayer or invocation dedicated to a deity. It was purely for religious purposes and didn't teach any spell.
 * A detailed ritual or offering to that deity.
 * A new ritual, or a modification of an existing one. For example a ritual to remove vermin from a temple, or a fastest way to learn fro the deity the name a lay person should take upon assuming priesthood.
 * A collection of prayers teaching spells. They were ordered in ascending order of power, to ensure the novice's safety.
 * A closing prayer praising the deity. As for the opening section, this had purely religious purpose and didn't teach any spell. This section sometimes contained drawings of approved holy symbols, designs, of glyphs.

Notable Holy Books

 * The Argyr: A magical crafted of adamantine and plated with electrum, containing sacred spells of the Gondar faith.
 * Balance of Belaros: This holy book dedicated to Tyr was a set of magically floating bronze scales, which could be used to exchange offerings for spell scrolls.
 * The Black Book: This very tall book was dedicated to the goddess Beshaba. It was said to suck the vitality from its readers, and to have the ability to make undead creatures disappear altogether.
 * Chanting Chain: This unusual holly book dedicated to Talos had the appearance of a massive steel chain, whose links were large enough for a child's head to pass through.
 * Crystrum of Tranquility: This crystal sphere revealed spells to the followers of Eldath when immersed in running water.
 * Flame of the Spirit: One of the most holy relics of the Tymoran faith, this amber gemstone shaped like flame would transform into a tablet revealing spells in the hands of the faithful.
 * The Glarathra: Chauntea
 * Gorothir's Girdle: Shar
 * Helm of Helm: Helm
 * Key of Faith: Oghma
 * Lash of Loviatar: Loviatar
 * Leaves of Green: Silvanus
 * Mask of Mysteries: Mask
 * Mighty Rune of the Master: Deneir
 * Moonweb: Selûne
 * Orglara: Umberlee
 * Red Book of War: A massive holy book dedicated to Tempus, whose covers were made of beaten armor plates.
 * Sash of Sune: Sune
 * Scepter of Mystra: Mystra
 * Silver Supplicant: Auril
 * Testament of Vraer: Kelemvor
 * Tome of Morning: Lathander
 * Tome of Torment: Ilmater
 * Tome of Universal Harmony: The most holy book of the Deneirrath faith, whose spells could only be learnt by the deity's Chosen.
 * Veloghon of Vigilance: Torm
 * Vorthryns Archivir: Azuth
 * Wythyndle's Round Book: Bestowed by Milil himself to its clergy during the 10 century DR, this book contained several exclusive spells and had the ability to teleport itself around Faerûn.
 * Yornar's Trail Companion: Mielikki

In addition the following items were considered holy books despite not teaching any new spells to their readers, or despite not being dedicated to a specific deity:
 * Book of Exalted Deeds: An artifact of great power, this book wasn't dedicated to a single deity but was considered as the supreme written authority of goodness and virtue in all the multiverse. ;Book of Fangs and Talons: Malar
 * Book of Perfect Balance: A holy book that wasn't dedicated to a single deity, but was considered sacred by creatures of neutral alignment. Once read this book disappeared, and the reader would never encounter it again.
 * Testament of Jade: A relic of the Lathanderian faith, which granted its owner the ability to cast several divine spells on a daily basis.
 * Tome of the Dragon: The holy book of the Cult of the Dragon, whose members venerated dracoliches.