Back in the day when all books were covered with leather and the whole world was covered in goats things were just fine and dandy. Eventually bliss had to settle for simple. Leather needed to be conserved a bit. Enter: Millimeter bindings.
Millimeter bindings use a little less leather than full covered books because they use pieces that average (while varying in height) 30 - 40 millimeters wide. This method conserves leather while still giving books that swanky stature of being called a leather binding. Traditionally millimeter bindings are covered with paste papers.
Below is a copy of David Foster Wallace's This Is Water and a blank model featuring paste paper I made on my kitchen table.