Being a treatment of the art of magic for sorcerers and their ilk for Lamentations of the Flame Princess and similar old school games – in short some House Rules that suit my style of play a little better.
Each sorcerer maintains a spellbook which is a working journal containing the details of the spells he or she knows. Each spell consists of a complex geometric form or sigil that the caster must visualise as he or she reinforces the form with gesture and spoken incantation.
If the spellbook is lost or destroyed the sorcerer can recreate it but this will take time - one 8 hour workday per spell per level.
StudyingThe sorcerer must revise from the spellbook for at least an hour each day, practising forming the sigils. If the sorcerer is not able to do this - either because of time constraints or the lack of access to their spellbook - then spellcasting becomes a greater effort for them. They can cast only half the normal number of spells per spell level each day until this situation is remedied.
MemorisationThere is no need for a sorcerer to memorise specific spells for the day ahead. They are assumed to be familiar with all the spells in their spellbook and can cast them as required - assuming they have enough spell slots available.
Spell Slots and VitaThe spell slots available to a sorcerer relate to the amount of magic essence or vita they have access to, and more experienced sorcerers can use theirs more efficiently, reflected by the greater number of spell slots available
A higher level spell slot can be expended to cast a lower level spell with the excess vita being lost. Burning lower level spell slots to cast a higher level spell is possible but it will take a total of spell slots equal to the level of the spell being cast plus one.
Scrolls containing one or more sorcerous spells can be used in two ways. Either the sorcerer can transcribe the details of the spell they contain into his or her spellbook and thus add it to their known spells, or the vita contained within the scroll can be expended along the channels of magic created by the creator of the scroll and casting the spell (or one of the spells) written thereon. Once a spell is cast from the scroll in this way the details fade forever from the scroll.
If a sorcerer is in dire need and has a scroll available they can draw the vita from it to use for their own spells. If this happens all the spells on the scroll vanish at once but the sorcerer can use the vita in it as though it was a spell slot equal to the total levels of the spells written thereon minus one (so if the spell contains 2x 2nd level spells, it could be used up to give the caster a single 3rd level slot).
Other Sources of VitaSome items can be enchanted to hold vita either one a one use basis or reusable. An enchanted gem in a necklace for instance may hold a pool of six spell slots that can be used by a sorcerer at will until they are used up. Alternatively the gem may hold a single level one spell slot but this replenishes each day at dawn.
Evil sorcerers may find that acts of abominable cruelty and sacrifice release vita in their commission which explains why they resort to such horrors to power their dread rites.
(Here is a prettied up pdf version)