A nice way to protect your books with a slipcase.
This is from Hedi Kyle's wonderful book "The Art of the Fold" (in german: "In Falten gelegt").
Paperboard 300 g/m²: length x width (2x), (length+width) x thickness (2x), paper (e.g. craftpaper) (3t+4b) x (2b+h).
http://www.papierdesign.de