To say that Dungeons & Dragons traditionally uses “Vancian spellcasting” – in which spells are memorised, and then forgotten when cast – accurately identifies the inspiration for the magic system but mischaracterises Vance’s own work. The fact is that the method of spellcasting in question appeared more or less only once, in a single story in a much longer series in which various other forms of magic also appeared, and with much more flavour. The Dying Earth sequence, despite some problematic elements, remains one of my favourite mid-20th Century fantasy series, mashing up as it does classic sword and sorcery, a poetic temperament worthy of a Lord Dunsany or Clark Ashton Smith, and a wry picaresque sense of humour. Although Dungeons & Dragons nails the sword and sorcery style, it’s never really delivered on any of the rest, and so its take on what is “Vancian” is necessarily limited.
Thankfully, Pelgrane Press – named for a flying beast from the series – made their grand debut in 2001 with The Dying Earth, easily the best and most innovative fantasy RPG of the early 2000s. (Apparently John Tweet and Monte Cook put out some sort of early prototype version of Pathfinder the previous year, but I don’t recall it being especially fun.)