In the TV series <i>Dragnet</i>, detective Joe Friday used to say ‘All we want are the facts’. Joe Friday would have loved Brian Clegg’s books. Brian can be relied on to give you the facts, and nothing but the facts, on matters scientific, from the science of the human body to – in this case – the science of time travel. <i>10 Short Lessons in Time Travel</i> lucidly sums up the essential parts of this fascinating subject. Spacewarps and timewarps are both allowed by Einstein’s general theory of relativity, and both feature here, along with practical hints on how to build a time machine and the pros and cons of freezing yourself to wake up in the distant future. The bottom line is, time travel is theoretically possible, but practically very difficult. But 500 years ago, the same could have been said of heavier-than-air flying machines.

- John Gribbin, author of "Six Impossible Things: The 'Quanta of Solace' and the Mysteries of the Subatomic World",

Brian Clegg's guide to the theory and practice of time travel keeps its promise and is a highly enjoyable and informative read.

- Giles Sparrow, BBC Sky at Night Magazine