I recently finished Pawn in Frankincense by Dunnett. I know of one other book that can have the same effect on me, and it was written by Tolkien. The chess game and its horrific ending. How does one subject his character to so great a suffering? And how does the character survive? And how does the author live with himself? I don't know that I could.
In my opinion, one of the most devastating climaxes of prose ever written. "Say goodnight to the dark."