To summarize the rules from Blueholme:

1. The game uses the traditional, pick spells to “memorize” to fill spell slots and the spell is “forgotten” when cast. Several examples of the same spell can be used to fill several slots.
2. Both Clerics and Magic-Users must use spell books to memorize their spells
3. Spell Books are large and fragile and cannot be taken on adventures, only left at home and carefully moved from home to home.
4. Each level of spell is its own volume of spell book.
5. Clerics have all the spells from any particular level in their books.
6. Magic-Users use the INT-based chance to know spells/max-min number of spells chart page 8 to figure out which spells are in their book when they gain a new spell level.
7. It takes 1 full day studying from your books to refresh all your used spell slots.
8. Scrolls can be used to memorize spells to fill up used spell slots, without discharging the spell from the scroll.

House Rules, Clarifications and Setting Tie-in

Magic-users begin with a level 1 spell book. Dues-paying members of magic guilds receive a spell book from the guild when they reach each new spell level. If they aren’t in a guild, they must create or acquire a new spell book for 750gp times the spell level. Likewise, if a magic-user loses his spell book he must create or buy a new one for the same price. If a magic-user captures an enemy spell book, he may use it to study spells he knows, once he has cast Read Magic on that particular spell in the book. All magic-users begin play with 1 scroll of 1 spell from their first level spell book in order to allow them to travel and function as magic-users.

Clerics receive a level 1 spell book from their temple when they reach 2nd level and each additional time they gain a new spell level. If a clerical book is lost or destroyed, the cleric is issued a replacement, but is also assigned a penance task for failing his god. Spell books from another religion do clerics no good.

Spell books are large and fragile. Each volume fills an entire back pack or saddlebag. A person cannot carry more than 3 volumes (without some sort of magical help) in any circumstance. Carrying a spellbook automatically renders one at the Encumbered encumbrance category. Each day a spell-book is carried on adventure, roll 2d6, if the total is 12, the volume has been destroyed in some mishap. If the book is subject to any sort of water, magical or fire attack on an adventure, it is automatically destroyed. A book can be transported safely if packed securely in a locked chest, lain flat in a sturdy 4-wheeled wagon that travels on a road. If travelling well-packed in a ship, there is a 1 in 20 chance every 3 days that it will be ruined on the trip.