Re: Time travel - Speed of light
My recommendation
In Search of Schrödinger's Cat: Quantum Physics and Reality
by John Gribbin
Quantum: A Guide for the Perplexed and Black Holes, Worm Holes and Time Machines are both by Jim Al Khalili and both do a great job putting Quantum Mechanics down to the level of an 11th grade High School kid.
Schrodinger's Cat is actually a little outdated. Gribbin wrote the first one in 1984 and the second one "In Search of Schrodinger's Kitten's" in 1996. In contrast Al-Khalili wrote his in 1999 and 2003 respectively.