I hung this on a gray/blue wall over my son's desk in his room and the wall color showing through the bookcase is stunning.  It allows for books, awards, decorative accessories and more.  It is a very architecturally interesting element to an otherwise simple room.  We even have a task lamp on a shelf which shines down to his computer.

Pros: Can be mounted if you are handy and makes a great conversation piece.  Better than lots of staggered little shelves.