Vancian magic is one of the topics that old-school gamers love to argue about. Most love it, some hate it, everyone discusses it. Here's the core rules for spellcasting in ACKS: "During any single day, spellcasters can cast the number of spells of each level indicated on the Spells Progression Table for their class. Unlike other fantasy games, in Adventurer Conqueror King, spellcasters do not have to “memorize” or “prepare” their spells in advance; they can choose which spells to cast at the time of casting from among any and all the spells they know (see below). Once spellcasters have cast all of their available spells for the day, they must have 8 hours of rest and one hour of prayer or study before they can cast again." In the early days of the Auran Empire campaign that build ACKS, I was inspired to take this "free casting" approach by a comment made by Frank Mentzer in Dragonsfoot. Back in 2009, the great Mr. Mentzer wrote, "the lack of the Vancean restriction actually helped play, imho. Instead of trying to outguess the DM and pick a useful spell before the adventure, players felt more confident and more versatile, even with only 1 or 2 spells per day. The players of magic-user characters had more fun.... Ever see a magic-user take, and then actually use, a simple Light spell? It happened in my game. In the second session the 3rd level party coped with a terrible Troll thanks to a Levitate spell... which very probably would have been omitted in favor of a Web or something had we stuck with btb Vance. There are other examples with which I won't belabor you... but it worked and it worked well." (http://www.dragonsfoot.org/forums/viewtopic.php?f=11&t=10717&start=4455) We implemented free-casting into our own campaign, and found it had the same beneficial effects. However, we did not combine free-casting with the 1e/3.5e style of spellbook, in which a magic-user/wizard has nigh-unlimited capability to add spells to his spellbook. Instead, we built on a modified version of the spellbook rule in the Basic/Expert set: "Arcane spellcasters know only a limited number of spells, representing their personal collection of dweomers and enchantments. Each arcane spellcaster keeps a set of spell books, containing the magical formulae for each spell the arcane spellcaster has learned, written in a magical script that can only be read by the arcane spellcaster who wrote it, or through the use of the first-level spell read magic. An arcane spellcaster’s spell book can contain a maximum number of spells equal to the number and level of spells listed for his level, modified by his Intelligence bonus. For instance, a 3rd level mage is able to cast 2 1st and 1 2nd level spell per day. If he has 16 INT (+2 modifier) he can have up to 4 1st level and 3 2nd level spells in his spell books." Thus, mages have a very tight selection of spells available to them, especially if they have a low INT, but they can freely cast from that narrow selection as they wish. This makes them somewhat akin to 3.5e's Sorcerers, except that they do have spellbooks, and must find, research, or learn their spells. What if a mage wants to change his selection of spells in his spellbook? "An arcane spellcaster can rewrite the spells in his spellbook at a cost of 1 week of game time and 1,000 gp for each spell level. For instance, Quintus is a 1st level mage with INT 16. He is eligible to have 3 1st level spells in his spellbook. Over time, he has recorded read magic, shield, and sleep into his book. He finds a grimoire holding magic missile and decides to replace shield with his new find. This costs 1 week of game time and 1,000gp. He now has the ability to cast read magic, magic missile, and sleep, but no longer knows shield." Thus we retain the ability of mages to alter their selection of spells as they learn new ones, or to meet different or changing needs, but it's a much longer and more expensive process. This creates downtime, which is an important part of long-term campaign play. As for clerics, they too enjoy free-casting, but they also have substantially narrower spell lists that have characterized 1e-3.5e of our favorite roleplaying game. "Divine spellcasters receive their spells directly from the deity they serve, and they automatically know each spell of each level they can cast on the spell list made available to them by their deity (but not necessarily every divine spell in existence). The Cleric Spell List, below, represents a general list of spells that might be provided to clerics of powerful gods with broad spheres of influence (such as clerics of Ammonar). Because clerics gain their spells from a specific deity, however, the exact spells available for any given cleric could instead include a variant selection from this list combined with spells drawn from other sources; for instance, a deity devoted to healing may refuse to grant their cleric’s reversed healing spells, but might offer special curative spells available only to her clerics. Just because a spell is listed below as a divine spell does not necessarily mean it is available to every cleric. The DM will determine which spells are appropriate for any given cleric based on the power he serves. The Bladedancer Spell List, also below, is an example of a spell list for a divine spellcaster designed around a specific deity (Ianna, Goddess of Love and War)." One final rule regarding magic is the notion of the spell signature: While spells have general effects that are common to all who cast them, the specific sensory effects associated with the spell will vary from caster to caster. This specific sensory effect is known as the spell signature. A spellcaster should write a short description of the signature for each spell he can cast. For arcane spellcasters, the signature may be based on a particular school or style of magic, or simply be a reflection of the spellcaster’s personal taste. For divine spellcasters, the signature reflects the caster’s relationship with his deity. A character’s choice of proficiencies can be suggestive of appropriate spell signatures. EXAMPLE: Sargon pursues necromantic magic and black lore. His player decides that all of Sargon’s spell signatures will revolve around death. His magic missiles appear as shards of bone. His sleep spell places targets into a nightmarish slumber where they dream of hell. His lightning bolt is crackling blue-black energy. His wall of stone has the appearance of tombstones graven with the names of the dead. Using Spell Signatures is a great way to add character to your mage PCs and NPCs. It also broadens the "feel" of the spell list without having to make an inordinate number of spells. Sizzling bolts of red energy, crackling blue-black energy, and golden rays of light are all lightning bolts. There's some specific mechanics around Spell Signatures that let you identify the spellcaster if you know his or his school's Spell Signature, but you'll have to read the rules for that.
This one is a mixed bag of good and bad news, I think it would be much better to have
Usable spell: as always
Ready spell: in the number indicated (memorizable + Int Bonus)
Spell book: with a maximum number defined by intelligence (say Intelligence - spell level)
to change a readied spell you must spend time (1h/spell level?) and you must have it in your book
the rewrite thing sounds wrong
I like the ‘freecasting within a narrow selection’ idea. It allows improvisation without having ‘option anxiety’. It makes spellcasters less predictable, not a one trick pony.
yeah the idea is good and workable, but the idea of “rewriting” one own spellbook is counterintuitive
Thanks for the feedback! I agree that “re-writing the spellbook” is a bit counter-intuitive, but it might be an issue of phrasing? I haven’t really provided a setting-based (i.e. meta-game) reason to explain why a mage is limited to X number of spells, so I think that’s why it comes off as odd to trade in/trade out spells.
In my mind it has something to do with having to track astrological movements, various elemental powers, certain taboos to keep, etc. and mages of certain levels and Int are simply able to do more of that sort of thing. Switching spells is thus a matter of learning the new astrology, rituals, taboos, etc.
Fabio, I think your idea would make mages too powerful. One of the major balancing factors is their narrow selection, and downtime of just a few hours would topple that. That said, if you play it that way, please let us know how it goes!
I pledged so I think that I’ll explain this on the forum 
anyhow the downtime can be also of 1 week of prep time it’s not really important 
Magic Users - So combining Ryth Chronical spell selection with a Holmesian style “chance to Know” mechanic. Sounds good to me.
Clerics - spells limited to those given by divine providence - that’s a great idea, allowing for a lot of variability in Clerics without creating new classes.
I think a better solution to the “rewriting” issue is to increase the cost of adding new spells. To me, the idea of “forgetting” a spell to learn a new one is a bit inane, and it is one of the biggest complaints among players of 4E. The general feeling is that once someone knows something, they should know that something forever (barring powerful magics or brain damage).
I would suggest that you treat spell formulae as magic items; just as the fighter greatly increases in combat ability when he finds a magic sword, so too does a mage when he discovers a new spell scroll.
One possible tie-in to the above solution would be to use a spell point or fatigue system, wherein wizards can only learn spells of their level or less, but rather than cast three first level spells and two second level spells, the wizard can cast any spell that they know, but the higher-level spells are more draining, in that they cost more spell points or cause greater levels of fatigue. By using this method of spell casting, spells would still be differentiated in power by their level (and we could have more than nine levels of them), but wizards wouldn’t have compartmentalized brains which could only power X spells of level one, Y spells of level two, and so on.
Another possibility would be to require a wizard “equip” a spell before using it, so that he has to have the scroll of the spell he wishes to cast in-hand before using its magic. Sure, he may know a hundred spells, but he can only fit ten or so per scroll case, and he may only have one at the ready at any one time.
Or perhaps use an alternate spell storage system, such as runic carvings on a staff or tablet, so that a wizard can only carry around a limited number of spells among his whole repertoire at any given time. At higher levels, a skilled wizard would require fewer mental aids for his spells, and so he can fit more spells on his staff (less runes for each spell).
Yet a third option: allow wizards to cast any spell they know an unlimited number of times per day, but require rare and expensive components for each spell. Sure, this will add a large amount of bookkeeping for any wizard player, but it balances power levels in a sensical way.
It also can add a fun minigame aspect to play where wizards are constantly on the hunt for their components:
“Hold on, let me drain some of that dragon’s blood. I need it to cast my ‘heroism’ spell.”
“Okay, we need to go into the banshee infested hills. I need some of their hair to power my ‘death knell’ spell.”
etc
Just found this site… it seems interesting and I’d like to comment… why do wizards need to rewrite their spells at all? Once you learn your spells and you reach your full capacity of spells known, there simply isn’t room in your brain to learn more and you shouldn’t just be able to simply unlearn what you have learned with a week’s time and some money.
So I think it works well as you’ve got it minus the rewriting/relearning aspect. A wizard could still expand their versatility, by acquiring scrolls, and magic devices that can cast spells. In such a setup, the wizard expands his or her number of spells per day but only on a limited and finite basis.