steeldragons
Steeliest of the dragons
Good stuff - I've been taking the traditional approach in my 1e AD&D campaign, the only time an M-U player gets a free choice spell is one common spell, on level up, while in an arcane research facility, IF they make their chance to know % and IF they haven't already maxed out their 'known spells' limit.
Edit: Also I'm keeping the massive destructive magics rare, most NPCs will have more or less random spells in their books.
Very cool.
I do the same in my games too. Finding things like Fireball, Ice Storm, the Polymorph Other spell (which I still have/use in my world) and the like are simply...potentially too rampantly destructive or dangerous for an organized "responsible" mage's guild to give out to just anyone. Lightning bolt is far more common among wizards (given the, was it a 5' radius bolt? Which I basically flavor/narrate as a series of smaller/thinner bolts all branching off and rejoining that streak to the same target/limited targets).
But yeah, finding another mage's spellbook is likely to just have a random array of spells and highly destructive spells being among them is uncommon.