The GCHQ Puzzle Book

This collection of brain-teasers comes from GCHQ, the British intelligence and security agency, and is designed for readers who want a demanding workout. It follows an earlier volume and includes starter puzzles for newcomers as well as a tougher section for experienced solvers. The challenges draw on codes, logic problems and tests from the agency's archives. To mark the organisation's hundred-year anniversary, the book also includes short sections about its past, from its origins as the Government Code and Cipher School, through the codebreaking work at Bletchley Park, to present-day protection against cyber threats. Readers get a glimpse behind the scenes alongside the puzzles.