Well, who knows for sure? The evidence is fairly solid on Stuuthof Concentration Camp engaging in small scale production of soap from human fat - and then using it to clean up after performing autopsies on experimental subjects. They also made buttons out of the bones - again, that's fairly well established.
The "human skin for leather lampshades and book leather" largely comes from the trials around Ilse Koch - which is where things get murky. Ilse was pretty far out there in wacko land, by any standard, and was even at one point arrested (along with her Husband, who was the Commandant and Buchnewald) by the Nazi's themselves because, by all accounts, things had gotten pretty far out of hand even by their standards.
The history of whether or not it happened is completely up for debate, by respectable historians who've argued it both ways. It wasn't a mass production thing, if it happened at all.
Either way, referencing leather made from human skin is pretty dodgy stuff to bring up in some circles.
