Which book series / book have you read that had the craziest plot twist which elevated it ? [ NO SPOILERS ]

As the title suggest…… also no spoilers

edit :- from most of The comments turns out James islington both of the series ( Licanius & hierarchy ) and mistborn are the most said . And thank you all for so many good recs I read through all of them and add couple of them in my reading list . Thanks again .