My example isn’t a rewrite per se. However, when Robert Jordan died, Brandon Sanderson was hired to finish the final books in the Wheel of Time series. I love the first few Wheel of Time books but by the end Jordan seemed to lose direction. Sanderson not only finished the series (adopting the story’s approach to magic, etc, which is different than his own), but his last books are now my favorites in the series. In this way, his books are both a continuation and a rewrite.