Are there any series written by one author, then taken over by another when the first author dies, that get better under the new direction?

This title is so messy, apologies. I’m thinking of the trend for new books written long after the original writer who came up with the concept has passed. Sophie hannah writes Poirot novels, Anthony Horowitz has written Sherlock Holmes books, Jill Paton walsh continued the work of Dorothy l sayers etc. Are there any examples you think have been markedly better than the original efforts?