Modern Book Sizes Are Based on Sheep
ok, so basically we already knew that, but I love the neatorama kindle quote:
The whole sheepskin, flattened out and folded in half, is one common size. Fold it again, and it’s another size. All of these sizes and dimensions are still being used by printing houses in the 21st century. The Kindle, for example, is the size of a sheepskin folded over three times.