This article linked to is probably stretching it a bit for a book blog – especially given that you have to basically destroy books to accomplish the secret compartment. But it is made out of books – so that’s the connection. The link below is to an article that looks at how to build a secret compartment out of books.

For more visit:
http://www.lifehacker.com.au/2013/06/make-a-secret-compartment-out-of-multiple-books/