This is kind of brilliant. Torafu has designed a new notebook with a slightly obtuse angle on one side. Why would they do this? So that the notebook sticks out from the rest of the books, reminding you of its exact location. Not planning to revisit the notebook for a while? Then simply flip it over so that it rests on its flat edge and it will become camouflaged between its other neighbors.
Simple idea, brilliant results!
source: Torafu website