Not asking about the mechanics, but about the "lore" for the purpose of eg novel or short story.
Before, memorisation was represented in the following, IMHO coherent way:
You prepare a spell and mark it in your own mind, and can "feel" it as an entity of its own. To cast it, you find it in your mind, visualise it and release it using trigger components/words/gestures. Each spell is its own thing: if you want to cast it more than once, you have to memorise several instances.
Now, I'm not sure of how it should work. If it was presented in any Forgotten Realms novel, I've missed it.
The mechanics say that you prepare ("memorise", kind of) several spells beforehand. But then you can decide to only cast one of those prepared spells (of the same level), a limited amount of times per spell level.
How can this be justified, for a novel for example?