DIY Secret Hollow Book.

How to make a secret hollow book:

You'll also need:

1. Elmer's white glue
2. a container to hold glue solution (I've chosen a film canister)
3. X-acto knife, and/or box cutter. Both if you have them
4. brush to apply glue solution
5. pencil/pen
6. ruler, or other rigid straight edge

Link (via Geekman)