Providing examples of Einstein’s theory of relativity at work today (why satellite clocks run faster than ground based ones), Cohen documents a number of different views about the possibility, inevitability and futility of time travel. This very short romp through topics like string theory, wormholes and light will make you think.
While not a DIY handbook for construction of my own T.A.R.D.I.S. this was certainly worth the quick read.