Gleick's book "Time Travel" is really a long-form essay that takes a look at the whole concept of Time Travel (and time, itself) through the lens of time travel's various incarnations in science-fiction and pop culture. It starts off with an at-first surprising point that the modern understanding of "Time Travel" didn't really exist until H.G. Wells put it in the public's mind in the early 20th Century. This timing was not-coincidentally around the time when Einstein was also changing the way we think about time, and humanity began to have a new and exciting and/or terrifying understanding of the universe around them.

By examining the formulation of time travel through the years in pop culture, Gleick gives a fascinating insight into the science of time (touching on topics such as relativity, black holes, Feynman's work, etc.), the philosophy and psychology of time, and culture in general (the rise of time zones, the lack of 'time' as a prevalent idea in the past).

It was also very thought-provoking how Gleick pointed out that the language and metaphors we use to describe time can be both useful tools and a cage in our thinkings. A quote that stood out to me about this specifically: "Everything was so unsettled about time. Philosophers, physicists, poets, and pulp writers all struggled. They were using the same word bag." Then considering the idea how different cultures even differ in what 'direction' time goes (e.g., we commonly think of the future as in front of us and the past as behind us, but these are merely constructs we adhere to) further makes you question everything you thought you knew about time.

Examples of other topics that have stuck with me since I read about them in "Time Travel" include the idea that memories aren't accurate descriptions of the past ('when' do memories even fall in the timeline, as the past or in the present that we're remembering them), how does that advent of internet and communication technologies affect perceptions of time (communication can be virtually instantaneous, or your 'present' reception of communication from me is actually from the 'past' version of me), the rise of time capsules as a way for people to communicate with the future, and the general questioning of how 'real' time is (what's the difference between the past and the future, does the past exist if it's unrecorded?).

The book is not long, but it's very idea-dense and challenging at times. You definitely need to use your full faculties while working through it-- but the thought-provoking ideas are worth the effort. There are some heavy topics (multiple worlds, eternity, determinism, free will), but if nothing else then reading this added a lot to my reading list in biographies of the main players and sci-fi stories referenced.