"I think I can safely say that nobody understands quantum mechanics," said Nobel prizewinning physicist Richard Feynman in 1964. Jim Al-Khalili agrees. Quantum mechanics was the most important scientific advance of the last century, and is fundamental to technology we now take for granted, from computers to the lasers in DVD players. But despite this, the quantum domain is "so astonishingly strange that it even makes tales of alien abductions sound perfectly reasonable". Al-Khalili takes the reader on a journey through this microscopic world, where subatomic particles behave differently depending on whether they are being observed, where they can be both wave and particle, and where two quantum particles can remain in touch however far apart they are  an idea Einstein wrongly dismissed as "spooky action at a distance". In this reissue of a 2003 publication, with mini-essays by scientists Frank Close and Paul Davies, Al-Khalili succeeds in making the quantum world understandable. Well, almost.