This could go either way...
Mike Flanagan is a great writer / director, who has only made one dud film so far. He also seems to get what makes Stephen King's work tick, because he turned "Gerald's Game" into a really good movie (if anything, it's too faithful to King).
However, "Doctor Sleep" isn't a very good book. And, to be honest, Kubrick's "The Shining" was superior to King's novel.
So Flanagan is now is the tricky position of having to adapt a not-so-great book as well pay homage to Stephen King AND Stanley Kubrick, who both disliked the other's take on "The Shining".