Old School Open Book Spellcasting

I actually enjoy Vancian magic. I don't prefer it in every fantasy role-playing game, but I find it effective, interesting, and fun when it is employed appropriately. That is not to say it can't be improved. The following is a house rule I intend to use the next time I run Swords & Wizardry or earlier editions of Dungeons & Dragons.

Open Book Spellcasting

As per established rules, a magic-user may memorize a certain number of spells of various spell levels according to their class level. These spells, once cast, are "erased" from the caster's memory, but may be re-memorized given time and access to the right spell book or scroll.

A magic-user may, however, choose to cast directly from the spell book or scroll without causing the written spell to disappear (which is what happens when non-magic-users are able to cast a spell from text). To do this, the magic-user must read directly from the open spell book or scroll and make an attack roll versus an armor class equal to 10 + the spell's level (using ascending armor class). The magic-user is, in a sense, attacking the difficulty of the spell through brute force of will. If the roll succeeds, the spell is cast. If the roll fails, the spell is not cast and each subsequent attempt to cast it raises its armor class by 1. Normal difficulty is restored the following day. If the magic-user fumbles by rolling a 1, no more attempts may be made to cast that spell until the following day and the spell, if already memorized, is instantly forgotten.

In retrospect, the house rule I described in "Time for Another Spellcasting House Rule" in which the cost of casting an unmemorized spell is 1 hit point per spell level should probably be a variant of open book spellcasting and likewise require the use of a spell book or scroll. One could use both variants in the same game: one requires a roll, the other requires a sacrifice of hit points, but both require the reading of the written spell.