When I was a kid, spycraft was unbearably cool. One of the things I always wanted to make was a hollowed out book to keep secret stuff in.
Choosing A Book
One of the most important tasks is choosing the correct book.
The book must be large enough to contain whatever you want to hide. Also, it must be a book which would not look out of place on your bookshelves, but preferable be a bit dull, so people won't pick it up.
Oh, and always go for a hard-back.
None. This is a hardware hack.