So you want something that will help you get organized similar to the Storage In Stairs, but you find yourself too squashed by your massive book collection to move around your house. The Spacesaver Staircase Library merges the two issues, creating one solution.

The Staircase Library utilizes all of its space by creating book shelves in the space under each individual stair. Imagine all of the wasted space in a normal set of stairs. Not here.

— Andrew Dobrow 

Link