The sustainable design is not only one that uses materials, techniques and sustainable productive routine, but also what leads to the correct behavior, which lends itself to the introduction of good habits, such as for example, to give the books read and referred you no longer need, instead of leaving them to dust on a shelf.
I know of an apartment building in Berlin where, in addition to bins for recycling, there is always a box of books available to those who want to collect them and read them: a sort of bookcrossing condominium organized.
Primer B, Designed by Spanish designer Joan Rojeski, Follows this trend and fuses into a single object the typical condominium mailboxes, with a normal bookshelves. Next to each box is the space to support the volumes that you want to make available to the community, or a specific tenant. A very good idea to restore meaning to the sad boxes nowadays only seem to collect bills and advertisements, and less personal messages.