Yes, was it Pillars of Eternity that had actual spell-books for wizards that you could add to over time and also loot from other wizards and use instead or as well? It's a while since I played it, but do remember some game having something like it and enjoying the flavour it gave.
Of course, BG3 would have to 5e-ify it but I agree that something that brought the bookish nature of wizards to life would be great. Them actually having an item called a spell book would be a start, but then I guess you'd have to do something with it.
