Kara Witham uses a scroll saw to expertly cut-out books so they can secretly hold a flask. From her website:
The first chapter of Secret Safe Books was written in 2009. Kara was working a day job as a gallery guard for the Chicago Museum of Contemporary Art. Born out of many idle moments in the galleries and a lifelong love of books, the idea for Secret Safe Books was born. After shifts at the museum, Kara would click around the web researching methods of hollowing out books. She started out with a simple X-Acto knife and a lot of patience. Later, Santa brought her a scroll saw to help speed things along.
Next chapter ~ From the very beginning Secret Safe Books was a huge success. Kara's day job was history in less than a year and after the plot was clear that crafting book safes would balance the books, John wrote off his day job to work full time at Secret Safe Books.
They sell for about $50 – $60, and the flask is included, making them a great gift.