Mounting shelving is an excellent option for the bibliophile. Feel creative: put the shelves above the doors, under the stairs, or anywhere else, as they would be reasonably fit. This is a great way to store books without taking up space on the floor; spaces too.

The picture above shows the proper operation of the built-in shelves. Geometry adds a clean, crisp look to the space, and the shelf above the door proves that you can install a shelf anywhere if you're entrepreneurial enough.