I like this door shelf system better

This one looks nicer since the “shelf” part can be seen on the outside.  This would be nice on a closet door.  I also like how the shelf system sticks out a little bit from the door with quarter round.  Note, both of these solutions use solid core doors, most interior doors are hollow.

http://www.home-dzine.co.za/diy/diy-storage-in-door.htm