This small floating bookshelf is my solution to the all too common scenario of not knowing where my journal is or the book I am currently reading just cluttering up the desk. So, with a problem, an idea, and a few minutes in Fusion 360. Voila!
The shelf is mounted to the wall using three 3 lb command strips. So it will not hold very much weight, but then again, I only designed it for a couple of books. Any larger and I would not have had room on the print bed.
At 0.3 mm, this took about 8 hours to print on my Monoprice MakerSelect. Of course, this will differ with your settings. As far as the orientation goes, I recommend printing with the open rectangular face DOWN on the print bed. This makes it possible to print without supports.