A defence of Read Magic
The prompt is the discussion here at Like Being Read To From Dictionaries on the point of the Read Magic spell, and possibly a lack of clarity in the rules. I think Nagora gets it.
What's Read Magic? Put simply, in OD&D etc. just looking at magical script - at the text of a spell on a scroll say - isn't enough for a spellcaster to read it, and, if it's a spell, to learn it: it needs to be deciphered first, i.e. translated from the system and even the scrawl of the writer, a little like understanding a prescription maybe. There's a spell for that - Read Magic - but it means forgoing another potentially more useful spell to learn it.*
If we're talking gameplay benefits only, two seem clear. First, it delays gratification. Find a scroll, even a tome full to bursting, and if you don't have the tool, you just have to wait, hold tight and dream of what could be in there. What if you never find out..? That's D&D.
Second, if you can't decipher it, and suddenly need a translator or a teacher, it means a trip back to civilisation, new investigation, maybe a quest to weave in: a trip from village to town, or a journey to a regional hub, maybe to a major city or a new realm, or an expedition to the edge to find a recluse or radical. What can the party combine it with? What might happen out of the blue, and what's over that border, that hill..? What's that?
That plays to the resource management aspect of the game too, one feeding the other.
It makes magic more precious and it promotes the exploration at the heart of the game.
For a one-off game, your magic-user might take Sleep, Magic Missile. For a campaign, you're going to want Read Magic as soon as the breathing space opens up, especially if you're dreaming of the ancient lores, setting up a laboratory and weird new technologies.
Battlefield power gain
Off on a tangent then, for non-tactical roleplayers or other not-onlies, what if this reading idea was adapted to skirmish gaming and bigger, even where one-off battles are more common? It might not work in so expansive a way - one trade-off could be in positioning.
Imagine a rule: when a wizard, psyker etc. is killed, the model is left in place. A wizard or psyker of another force, even of a whole other background, can then come and study and/or drain the body under fire: a test can be made and a number of powers absorbed.
Think how much dynamism it could add to a game. Do you risk moving up or not? More importantly, if you needed a specific power to be able to do it, would you make space..?
* App as magic spell? With the size and scope of some spell lists - check - and potential for creation, maybe._