This is intended as a hidden doorway, but it's a reasonable way to design closet doors. That's because you're not expecting furniture to be placed in front a closet door. So, adding shelving makes use of that otherwise dead space.
DIY Bookshelf Door, remove and store original apartment door, replace with bookshelf door, and put original door back when moving out.
A flush-mount Murphy Door kit: built-in bookcase/secret passage!
Library gallery shelves hide secret bathroom and there's gallery bed space above (Emma Burns' barn)
Replace a closet door with a bookcase door. Great idea to hide the water heater. No more ugly, never touched water heater door.