Man, I wish I had been in Lisboa in 2006. Why, you ask?
This is why:
Yes, that is an octagonal building made of books. Created by Slovakian artist Matej Kren, the structure was installed in the Modern Art Center in Lisboa in 2006 and dismantled six months later. According to the original Inhabitat article where I first saw this posting (link courtesy of Shelf Awareness, again), it is a "symmetrical, enclosed room of stacked literature."
The books used were all borrowed for the installation and returned to the Calouste Gulbenkian Foundation when it was taken down. Now that's reduce, reuse and recycle.