You are probably already familiar with the classic “Secret Book Compartment” project. There are variations of this project all over the internet. There have even been a few version that been featured in Make Magazine articles as well as on the Make YouTube channel.
The basic concept of a secret book compartment is simple. You hollow out a large book and you use the cutout space to hide stuff. Unfortunately, most versions of this project have one major problem. You can only hide objects that are smaller than your book. However it is possible to hide larger objects by combining multiple books into one large multi-book container.
Complete instructions can be found at: http://www.instructables.com/id/Multi-Book-Secret-Storage-Compartment/
See the full series here.