Everybody loves a good mystery, and an unsolved mystery is even better. Sometimes, the questions can be more interesting than the answers. The Search in Extraterrestrial Intelligence [SETI] has recently hotted up, with a whole new wave of research going to show that we will always be fascinated by what we don't understand. Was 'The Wow Signal' a radio transmission from deep space? Or was it the resonating frequency of a passing comet?

Often, it can feel as if professional explainers of all stripes want to put an end to anything mysterious in life. But thankfully not everything in life can be nailed down, sucked dry of its secrets and turned into a factoid. Mysteries do still exist - and unsolved mysteries continue to tease us.

The 20 mysteries in this book explore a broad spectrum of strangeness. Some, like the sudden disappearance of the sailing ship Mary Celeste's crew, have gained universal currency. Others - such as the Kryptos Sculpture - are much more recent and less well known. Cryptids like Bigfoot and the Loch Ness Monster teeter on the boundaries of probable and improbable, hoax and reality, fact and fiction. Whether it be the intrigue of lost civilisations, like Göblekli Tepe in Turkey, sensationalist interest in The Zodiac Killer, or the elusive Shugborough Code that neither Dickens nor Darwin could crack, each in its own unique way presents a challenge. Sceptic or believer, the fun lies in probing them.