Floating bookshelves are the new rage. You can make them at home for as cheap as you wish. This is about the same as my floating DVDs tutorial, only with books, and I actually made these when we first moved in because it was so simple and I needed to get started on decorating. I just haven't gotten around to posting here.
You'll need some hefty, hardback books that you don't mind cutting into and gluing, scissors, short self-tapping screws, and two L brackets per book.
Measure and place the L brackets at equal distances.
Trace the L brackets and cut away just enough pages to have them sit flush when the book is closed.
You might have to cut into the cover itself to let the book sit flat against the wall when hung.
Screw the L brackets to the pages and then glue around the edges and glue the covers shut.
Let it all dry.
Then hang! Now you have homemade floating bookshelves.