Review by Alexandra Witze
As any fan of Doctor Who or Marty McFly can attest, few areas of science excite quite as much public interest as time travel. Step into a police box or a DeLorean, flip a switch, and you’re off to change the world — or perhaps save it.
Would-be time travelers now have two new relevant guides to the promise of time machines. Which you might prefer depends on just how much you wa