I was hoping this book would discuss more of the science concerning the possibility (and unpossibility) of time travel, but he covered more of the older science fiction that discussed time travel.
It all starts with a discussion of the H. G. Wells book, The Time Machine, that was published in 1895. That seems to be the impetus for much/most /all? of the time travelling science fiction that follows in his footsteps. I’ve not had the pleasure of reading the Time Machine, but now that I know it exists, I will give that a read.
He then goes on to talk about and explain how other science fiction authors address the concept of time travel in new, different, and unique ways.
The two chapters that cover more of the science and philosophy of time travel are Chapter 11 on Paradoxes, and Chapter 12 on What is Time. The main paradox that is discussed concerning time travel back in time, is the problem that one could kill their grandfather. Personally, I don’t think that one can not circle back in time to affect the present. Time operates like a function on a graph. For every point in time along the x axis, there can only be one y answer. Like a mathematical function, time is not allowed to backtrack.
But, it may be possible to jump to the future. All one needs to do is travel at the speed of light, or nearly the speed of light, and one can essentially travel into the future while aging very little. The main problem is that it takes a huge amount of energy to get a mass of any weight close to the speed of light. This was mentioned, but it was not talked about all that much.
If you want to get an overview of the science fiction of time travel, this is your book. If you want a scientific overview, this will have pieces and parts, but that is not the focus of it.
For a more in depth look at the concept of time, the Order of Time by Carlo Rovelli, may be better. I read that book a couple years back, but I found it to be a little obtuse. I seem to agree with many of the people who gave that book 3 stars.