One of the most aggravating things about playing a magic-using character in 2nd Edition D&D was the spell book limits. Some groups ignored them, giving magic user characters a fantasyland Kindle, with full access to any spell they wanted, while others insisted on page limits, chances of correctly inscribing spells, and that worst of things: the travelling spellbook.
However, the nature of the transmission of magical books, and the condition of medieval book making, means that huge books with aggravating page limits (and having to copy things out themselves) were precisely what historical sorcerers would have had to deal with.
The Medieval Book
In Medieval Europe most books were made from parchment – a writing surface made from stretched and treated animal hide. Paper became available from the 12th century, but only avant-garde writers seem to have used it. Most monastic scribes historically stuck with parchment, so depending on the character of magic users in your game, they might use either, with the benefit that parchment is more durable, while paper was thinner and so more pages could be fitted into a book.
Books would have been arranged into bifolia (folded double leaves) sewn into quires, which would be squeezed between the bindings in groups of around twenty. Most quires in England seem to have been six double-leaves, while continental book binders preferred four.
The binding itself would have been made of either a stiff parchment sheet stitched around the quires (cheaper and lighter), or highly decorated/leather bindings wrapped around wooden boards (more durable, but far heavier). Bindings were often unique to a certain binder or a certain city, as would be the tooled figures they used, allowing a knowledgeable bibliophile to track a book to a certain library or bookbinder.
Finally, a binding could have various additions for utility: bosses on the corners to protect the binding, clamps to keep the book shut (this was incredibly important with parchment books since their pages would curl over time), and metal studs called feet on the bottom of the book to protect it from damage when being read upright.
Add to this the occasional book with a ‘treasure binding’ – a highly ornate binding involving gold and/or jewels – and you could find yourself with a huge, extremely heavy volume that really wasn’t portable.
Getting a Spell Book
Universities would have been a melting pot of Latin-reading scholars who would often have been inducted into a token clerical role like Lector or Exorcist. This would furnish them a basic education in ritual, and the means to understand Latin magical texts that had come through cultural meeting points like the city of Toledo, where magical texts from the Arab world would be translated into Latin. William of Auvergn wrote of the problem of magical texts in Universities during his time as Bishop of Paris, condemning the use of Necromantic texts amongst scholars.
Monasteries seem to have acquired great numbers of their magical books from donations by private collectors, and those taking holy orders after a life outside. When John Ergholme donated 300 books to the Austin Friars of York, his collection included major magical texts like the Books of Solomon and the Sworn Book of Honorius. When clergyman John of London joined the Augustinian Friars at Canterbury, he ‘donated’ a collection of his own books, including magical books such as the Ars Notoria and Liber Vaccae, which seem to have remained for his own use.
With the growth of literacy even those outside the establishment were able to get their hands on magical books. In 1593 a French soldier-turned-cobbler called Noël le Bragard was arrested for magic after becoming known as as healer and magician. His journey into magic had started when he’d found that one of the town gatekeepers owned a book of magical spells to find treasure and gain love, but had refused to loan it to him. Eventually, he had met an old woman who had kept a chest full of magical books and papers which he bought from her, copied, and sold to a young nobleman.
Le Bragard’s collection included major books of the time, including Agrippa’s Three Books of Occult Philosophy, the spurious Fourth book, and the Ars Notoria. In England, the Tudor astrologer-physician Gregory Wisdom said that he had inherited a magical book called The Practise of Drammell from his father. More famously, the London based doctor and sorcerer Simon Foreman owned several major magical texts, including The Picatrix, the Ars Notoria and the Liber Ratziel, going as far as to write that he had penned a book of Necromantic spells in the 1590s.
The Makeup of a Magical Book
Books could contain spells for many purposes, or be dedicated to a specific goal. The medieval Liber Vaccae contains pseudo-scientific processes for making magical creatures who can be killed in various ways that grant special powers to the magician. The much-imitated Ars Notoria was a book of spells to quickly grant magical knowledge to the user without their having to study, while the Picatrix was derived from an Arabic manual for making various scientifico-magical gadgets (rings, potions, bracelets or periapts).
Other books, like the Clavicle of Solomon, contain varied spells with varied purposes. One version found on the Twilit Grotto site includes spells to find thieves, spells to create love, spells to cause invisibility, and spells categorised by broad theme, like ‘experiments of grace and favour’ and ‘experiments of hatred and destruction’.
Finally, there would be the category of spirit books, designed to teach the sorcerer who to conjure spirits for various purposes. These were ubiquitous by the later middle ages and early modern period, with common editions being copies of the Lemegaton (a Solomonic book), the Centrum Regnum (a book containing the instructions for summoning one hundred spirits, often copied with a different title if there were fewer spirits), and the spurious ‘Fourth Book of Occult Philosophy’ wrongly attributed to Agrippa.
And even in places where magical books were common, there might not necessarily be a free choice of available spells: the Augustinian abbey at Canterbury was probably one of the most free places of learning for magic in England (after it was dissolved, John Dee bought their library and used it to create his Enochian system of magic) and their collection of magical books only ran to fifty. For European magical practitioners the process of learning new spells would have been a risky process of following rumours and chance meetings.