I think I read the same book by Baron von Mullenheim-Rechberg. According to him, the ship was sunk by the crew, not by the RN. The RN had used a huge number of ammunition and torpedoes, and yet the ship was not sinking. Due to German sub fear and low fuel the RN was deciding to leave the area, as Bismarck was practically destroyed, on the deck nothing was left in any working shape but shot to pieces. Well, this is one side of the story. But it seems the torpedos could not sink the Bismarck with the hull made of "special" thick steel?? I know there are several views of what happened and how the Bismarck sunk but I think the Baron said they sunk the ship themselves in the end. Also with the first Allied shots the fire command post was destroyed so the Bismarck was not capable to direct its shooting. Also one or two gun turrets were hit as well, as far as I remember.