The Secret Life of Codes: How to Make Them and Break Them (Murderous Maths)

Using a host of hilarious characters, Kjartan Poskitt presents all the tricks, tips and shortcuts to maths they don't teach at school. Readers will learn how to encode and decode their own messages in as many ways as possible. Can you see this very last paragraph is coded? (Read all the fourth words). The book demonstrates other codes you've probably never really been aware of. Stop waiting therefore and go for it.