RD: Oh, hey, I thought this book felt different! Turns out it's made of leather! TS: Back before paper became more common, they used leather to bind books!
TS: However, even nowadays, there are places that will make leather bindings on request, or even re-bind a book for you! (RD: Neat!)
TS: …I even read once about a book that was bound with leather made from human skin… SS: Hahaha, you scaredy-cats!