Michael Moorcock's Elric Saga might work
Steven Brust's Taltos (Dragaera) novels have him as an accomplished witch, and mediocre sorcerer in the first book (starts medias ras) and his learning sorcery and witchcraft isn't too belabored
The second half of Zelazny's Amber books, which revolve around Merlin have him start at pretty much the zenith of his learned magic capabilities
|