You weren't going to read War and Peace anyway.

Not all of us can be hiding a rock hammer we use to tunnel through the walls of our cell, a secret can of microfilm containing the secrets of the US government over the last half century, or a computer disk copy of a much maligned garbage file. However, a hollow book might come in handy to hide a key or important documents we'd like to see a potential intruder never find. Here is a do-it-yourself tutorial to create a hollow book that anyone could find a use for.

How to make a hollow book. (wikihow.com)