Magi open valences in their mind that attract and store magical energies (aka memorize spells into spell slot). To do this they study complex mathemamystical formulae (aka spell book). Each valence is unique and it is not possible to open two identical ones. (aka no duplicate spells). It takes about a night's rest to accumulate enough magical energy (aka cast each spell 1/day). These energies are expended when spell is cast, but, the valence remains open (aka spell book only needed to change "load out"). These formulae may be written in any language, but most grimoires, at least the good ones, tend to be written in ancient, obscure, and/or diabolical languages (aka no read magic required). These formulae are not magical in and of themselves (aka no scrolls). With a source of concentrated mana to fuel spell in place of valence energy, a formulae may be slowly followed/recited (aka 10gp/lvl & 10min ritual casting).
[I make frequent use of a 2d6 mechanic where player rolls 1d6 and DM rolls 1d6 (in secret). The player will have some idea of the total, but not absolute knowledge. I use this for various rolls below. I picked this up from some blog post where it was used for reaction roll. In addition rolling "doubles" indicates some special (odd) occurrence from bad (snake eyes) to good (boxcars).]
Spell formulae maybe be copied
It takes a great deal of skill and time to copy formulae. Ruining the copy during this process is common. There is always the chance of introducing an unintended and unnoticed alteration. The Magus may continue spending time and money until they create the number of copies desired.
One day and d4*25gp per roll: 2d6 + mods >= 7 copy of formulae created "doubles" - Funkyness from bad (12) to good (2) +X Int Mod -1 spell is not known -2 transliterating spell from one language to another -4 transcriber does not know language spell is written in
Some example "doubles"; 12, error in transcription, spell will explode (d6/lvl, centered on magi) when cast. 10, spell will have opposite effect. 8, spell will fizzle. 6, spell's effects won't manifest until d4 rounds after it is cast. 4, weird but not that beneficial change to spell. 2, spell improved (better range, duration, effect).
Spell formulae must be learnt
Learning a formulae, which is required to cast spell, requires only time. Magi "learn" a given formulae after a number of "research points" equal to 10*spell level is accumulated.
One day per roll (reset to 0 if one week passes without study) 2d6 + character level + INT Mod research points accumulated "doubles" <= spell level, roll on Formulaic Research Mishap Table Base difficultly 10 * spell level research points. Multipliers: .5x With tutor, access to extensive library, or the like .1-1.0x How well understood is formula's language
This same process can be used for other research, magic item creation etc. Additional researchers are possible. Add their level(s) and Intelligence modifier(s) but still only roll 2d6. Inventing new spells, creating magic items takes more time and costs money. Typical spell research; d4x days uninterrupted study and d10*100gp per roll (reset to 0 if four continuous weeks pass without study)
Formulaic Research Mishap Table
d20 1 "Formulaic Magic is relatively Safe", roll on Heinous Blunder Table, but effects only last d6x days. 2 Unwanted magical discharge destroys d4x nearby formulae. 3 "Whoa that was intense", wake up d4x days later. 4 "Blammo!", take Xd6 damage (X=spell level), laboratory needs rebuilding. 5 Research attracts a knicker fairy which now lives in your pants. 6 "I am a meat popsicle"; Mental breakdown, worthless for d6x days. 7 "Who set the roof on fire?" 8 "Who set me on fire?" d6 cumulative damage per round until put out. 9-11 A kindly Magus offers you assistance; send them packing? Yes; research failed very next day... No; roll d4 1) Robs you instead. 2) Is an incompetent idiot and kills himself in process of ruining your research. 3) Spy for an enemy. 4) Actually helps! d6x research points. 12 Brain is mental mush, can't memorize spells for d6x days. 13 Develop minor psychosis, lasts d6x days. 14 Roll on d10,000 magic effect table. 15 Research ruined when peasantry with torches and pitchforks come round to put and end to your "deviltry". 16 Burnt out; no Formulaic Research for d6x weeks. 17 Waste d4 more days of fruitless research. 18 "Note to self; brandy good, research good, together bad." 19 Succumb to exhaustion and sleep for 8+d6x hours. Wake up refreshed with desire go outside, take a walk, see the Sun. 20 "We learn from failure", re-roll to determine nature of that failure but formulae is learnt/researched.
Heinous Magical Blunders Table